Tuesday, August 23, 2011

Mineral M


THE MINERAL MACPHERSONITE

 

  • Chemistry: Pb4SO4(CO3) 2(OH)2 , Lead Sulfate Carbonate Hydroxide.
  • Class: Carbonates
  • Uses: Only as mineral specimens.
  • Specimens

Macphersonite is named for a mineralogist at the Royal Scottish Museum, namely Harry Gordon Macpherson. It was named as recently as 1984. Macphersonite is a cousin of the more well known although still scarce leadhillite. The two minerals are dimorphs. A dimorph is a mineral that shares the exact same chemistry with another mineral, but their structures are different (di in latin means two and morph in latin means shape). Typically the different structures make the symmetries different as well. In this case, macphersonite is an orthorhombic mineral while leadhillite is monoclinic in symmetry. There actually is another mineral that has the same chemistry and a different structure from these two. The mineral is called susannite and is trigonal in symmetry. This makes macphersonite, leadhillite and susannite a complete set of trimorphs. All three minerals could be classified as sulfates due to their sulfate ion, but are here classified as carbonates due to the greater number and therefore more significance of the carbonate ions.

 

PHYSICAL CHARACTERISTICS:

  • Color is colorless, white, amber or brownish.
  • Luster is adamantine to resinous.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is orthorhombic; 2 m m
  • Crystal Habits include tabular or pseudohexagonal crystals.
  • Cleavage is perfect in one direction.
  • Fracture is uneven.
  • Hardness is 2.5 - 3
  • Specific Gravity is 6.5 - 6.6 (very heavy for a translucent mineral)
  • Streak is white.
  • Other Characteristics Some specimens are fluorescent yellow.
  • Associated Minerals include leadhillite, galena, anglesite, linarite and cerussite.
  • Notable Occurrences include the type localities of Leadhills, Lanarkshire, Strathclyde, Scotland and Aregentolle Mine, Saint-Prix, Saone-et-Loire, France and at least one specimen at Moon Anchor Mine, Maricopa County, Arizona.
  • Best Field Indicators: Crystal habit, color, luster, density, fluorescence and locality.
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MAGNESITE

 


Magnesite does not ordinarily form good crystals, but can make up a substantial portion of some rock types. It forms commonly from the alteration of magnesium-rich rocks during low grade metamorphism while they are in contact with carbonate-rich solutions. Magnesite has the same crystal structure of calcite, hence its inclusion into the calcite mineral group. Many of the properties of magnesite are either identical or similar to those of calcite. However, the magnesium ion does not allow the carbonate ion (CO3) to interact as easily with cold acids, as the calcium ion does in calcite. This provides the best means of distinguishing magnesite from calcite. However, dolomite(MgCa(CO3)2) can be almost indistinguishable from magnesite.
 
 



PHYSICAL CHARACTERISTICS:
  • Color is white or gray, also tinted yellow or brown.
  • Luster is vitreous.
  • Transparency crystals are translucent to transparent only in individual crystals.
  • Crystal System is trigonal; bar 3 2/m
  • Crystal Habits are usually massive forms such as lamellar, fiberous and course to fine grained rocks. Crystals are extremely rare, but when found are in the form of rhombohedrons or hexagonal prisms with a pinacoid termination.
  • Cleavage is perfect in three directions forming rhombohedrons.
  • Fracture is conchoidal to uneven.
  • Hardness is 4 - 4.5.
  • Specific Gravity is approximately 3.0 (average)
  • Streak is white.
  • Associated Minerals calcite, dolomite, aragonite, strontianite and serpentine.
  • Other Characteristics: effervesces easily only in hot dilute hydrochloric acid.
  • Notable Occurrences include Austria; Bahia, Brazil; Korea; China; California, USA and many European localities.
  • Best Field Indicators are crystal habit, reaction to acid, occurrence and cleavage.


 

 

  

THE MINERAL MAGNETITE

 


Magnetite is a natural magnet, hence the name, giving it a very nice distinguishing characteristic. Explaining the magnetism is not easy but here is a go at it. Remember, electricity produces magnetic fields just as magnetism produces electic fields. Magnetite is a member of the spinel group which has the standard formula A(B)2O4. The A and B represent usually different metal ions that occupy specific sites in the crystal structure. In the case of magnetite, Fe3O4, the A metal is Fe +2 and the B metal is Fe +3; two different metal ions in two specific sites. This arrangement causes a transfer of electrons between the different irons in a structured path or vector. This electric vector generates the magnetic field.

 

PHYSICAL CHARACTERISTICS:

  • Color is black.
  • Luster is metallic to dull.
  • Transparency: Crystals are opaque.
  • Crystal System is isometric; 4/m bar 3 2/m
  • Crystal Habits are typically octahedrons but rarely rhombododecahedron and other isometric forms, most commonly found massive or granular. Twinning of octahedrons into spinel law twins is seen occassionally.
  • Cleavage is absent although octahedral parting can be seen on some specimens.
  • Fracture is conchoidal.
  • Hardness is 5.5 - 6.5
  • Specific Gravity is 5.1+ (average for metallic minerals)
  • Streak is black.
  • Associated Minerals are talc and chlorite (schists), pyrite and hematite.
  • Other Characteristics: Magnetism stronger in massive examples than in crystals, striations on crystal faces (not always seen).
  • Notable Occurrences include South Africa, Germany, Russia and many locallities in the USA.
  • Best Field Indicators are magnetism, crystal habit and streak.


THE MINERAL
MALACHITE
  • Chemistry: Cu2(CO3)(OH)2, Copper Carbonate Hydroxide.
  • Class: Carbonate
  • Uses: As mineral specimens, an important ore of copper, as an ornamental stone, a pigment and for jewelry.
  • Natural malachite mineral Specimens

Malachite is a famous and very popular semi-precious stone. It is named for the Greek word for "mallow", a green herb. Its banded light and dark green designs are one-of-a-kind, and give it a unique ornamental quality unlike that of any other stone. The light and dark green bands are so distinctive that malachite maybe one of the most easily recognized minerals by the general public. A popular design of ceramic ware which imitates this banding is named after the mineral malachite. It forms the banding from subtle changes in the oxidation states of the surrounding pore waters, but the exact mechanism is still not well understood.

Tumbled stones of malachite are possibly the most popular tumbled stones ever and are sold in litterally every rock shop around the world. Carvings and figurines of malachite are almost as common. A skilled craftsman can make the concentric malachite bands follow the curves of a work of art like contours on a rugged terrain. Although malachite art is not as precious as jade; it is hard to argue that it is less beautiful.

Malachite is also popular in jewelry, Native American Southwestern jewelry especially. The stones inlayed in silver make a nice variance from the traditional turquoise jewelry. Instead of competing, the two green stones tend to compliment each other when placed together in the same settings. Other stones such as coral, mother-of-pearl, azurite, jasper and onyx used in the typically handcrafted jewelry also compliment malachite's green colors.

Although its massive carvable forms are well known, its crystalline forms are much rarer and only recently becoming widely available to the average mineral collector. One of its more unique habits is its fine acicular crusts and tufts. At times appearing as a mat of thin hairs or as a carpet of green velvet. Another unusual habit is its stalactitic habits such as pictured above.

Many beautiful specimens of malachite contain special combinations with other minerals. Such combinations are some of the most colorful mineral assortments in the mineral world. They include such stunningly colorful minerals as dark blue azurite, sparkling black mottramite, baby blue chrysocolla, or rusty red limonite. So common is malachite that it is associated with almost every secondary copper mineral whether they are carbonate minerals or not. Malachite is found with many rare copper silicates, halides, phosphates, sulfates and carbonates such as duftite, libethenite, aurichalcite, sphaerocobaltite, kolwezite, shattuckite, atacamite, chalcophyllite, antlerite, conichalcite, rosasite, chalcosiderite, clinoclase, brochantite, graemite, liroconite, mixite and cornetite, to name a few.

Malachite has a mineral impostor called pseudomalachite. Pseudomalachite is a copper phosphate that has a massive crystal habit and color that are very similar to malachite's habit and color, although the two minerals have different structures. Pseudomalachite means "false malachite" in latin and is very rare compared to malachite.

Malachite is an impostor of its own. It frequently pseudomorphs the closely associated mineral azurite. A pseudomorph is a mineral specimen where the original mineral has been chemically replaced by another mineral, but the outward appearance is still retained. Pseudomorph means "false shape" in latin parlance. The transformation is fascinating and sometimes leaves a nearly perfect azurite crystal shape that is actually malachite. Often the transformation is incomplete and leaves a blue/green mineral specimen unlike any other. A gem trade name is used for ornamental stones with this combination called azur-malachite. See the azurite page for a more detailed discussion of the transformation.

 

THE PHYSICAL CHARACTERISTICS OF MALACHITE:




 

 

THE MINERAL MANGANBABINGTONITE

 

  • Chemistry: Ca2(Mn, Fe)FeSi5O14(OH),Calcium Manganese Iron Silicate.
  • Class: Silicates
  • Subclass: Inosilicates
  • Uses: Only as mineral specimens.
  • Specimens

Manganbabingtonite is a rare relative to the more common, but still scarce, babingtonite. The two minerals are part of a series. A series occurs when two or more elements can substitute for each other without much distortion to the crystal structure. Manganbabingtonite is enrich in manganese, while babingtonite is enriched in iron. Both minerals contain a certain percentage of iron and manganese.

Manganbabingtonite and babingtonite contain both divalent (+2) and trivalent (+3) iron ions. There is a difference in the size of these ions with the trivalent iron being larger. In manganbabingtonite and babingtonite these ions are segregated in the structure because of their differing sizes.The formula is written to show this relationship. The substitution of manganese only occurs with the divalent irons, since they are of similar size.

The differing charges on the irons causes a very weak magnetism that might turn the needle ofa compass. This can be very diagnostic since these two minerals can appear very similar to many other black, monoclinic, submetallic minerals. The magnetic effect is greater in babingtonite because it has more divalent irons.

 

PHYSICAL CHARACTERISTICS:

  • Color is brown to black.
  • Luster is vitreous, submetallic to dull.
  • Transparency: Crystals are generally opaque but thin crystals or splinters can be translucent.
  • Crystal System is triclinic; bar 1
  • Crystal Habits include short stocky prismatic crystalsor tabular to platy forms.
  • Cleavage is good in one direction and perfect in another, these are pinacoidal but are at near right angles to each other giving the appearance of rectangular prisms.
  • Fracture is uneven to subconchoidal.
  • Hardness is 5.
  • Specific Gravity is approximately 3.5 - 3.6 (somewhat above average for translucent minerals)
  • Streak is brown to gray.
  • Other Characteristics: Sometimes very weakly magnetic.
  • Associated Minerals are galena, sphalerite, diopside, hedenbergite, garnets, axinite, babingtonite, polylithionite and calcite.
  • Notable Occurrences include Santa Teresa Mountains, Graham County, Arizona, USA and Rudnyi Kaskad deposit, Sayan, Russia.
  • Best Field Indicators are crystal habit, color, locality, associations, cleavage and luster.


MANGANESE

 

  • Chemistry: Mn, elemental manganese
  • Class: Elements
  • Uses: Many applications for manganese.
  • Specimens

Manganese is named from a corruption of the latin word for magnestism; magnes, in allusion to its prinicple ore's magnetic properties. However, manganese crystals have yet to be found in nature and therefore it is technically not a mineral, although laboratory grown specimens can look like a natural stone.

The element manganese is an essential element in people's daily food consumption and has several industrial uses. Manganese is used in steel alloys to increase many favorable characteristics such as strength, hardness and durability. In fact steel can not be produced without manganese; it is an essential ingredient in the process. Manganese is also used to color glass an amethyst color. That is not so surprising since manganese is the trace element responsible for quartz's purple variety, amethyst.

Manganese coloring ability in minerals is well known and appreciated. Manganese is chiefly responsible for the wonderful colors in rhodochrosite, purpurite, rhodonite, serandite and spessartine to name a few. Unfortunately most manganese oxide minerals tend to be black. Manganese is extracted from the ore minerals pyrolusite and rhodochrosite. Manganese nodules on the sea floor may one day provide an economic source as well.

 

PHYSICAL CHARACTERISTICS:

  • Color is steel or silver grey.
  • Luster is metallic.
  • Transparency: Specimens are opaque.
  • Crystal System is isometric.
  • Crystal Habits include only lab grown specimens.
  • Specific Gravity is 7.44 (very heavy for a metallic mineral).
  • Notable Occurrences include only lab grown specimens.
  • Best Field Indicators are color and density.

 

 

  

THE MINERAL MANGANITE

 

  • Chemical Formula: MnO(OH), Manganese Oxide Hydroxide
  • Class: Oxides and Hydroxides
  • Uses: A minor source of manganese and as a mineral specimen
  • Specimens

Manganite was a valuable manganese ore when it was found in plentiful deposits. Now its rarity has relegated it to the standing of a minor ore dispite its high manganese content. Crystals are the chief indicator for identification. Only a few metallic minerals will have similar crystals (such as enargite) and these can be eliminated by means of comparing manganite's reddish streak and hardness. Pyrolusite is softer and has a bluish streak. If manganite is massive, it is difficult to distinguish it from other manganese minerals. Fine crystals of manganite can make a nice addition to a mineral collection.

 

 

 

 

 

 

 

 

 

PHYSICAL CHARACTERISTICS:

  • Color is black to steel gray.
  • Luster is metallic to dull in weather specimens.
  • Transparency: Crystals are opaque, translucent in only thin splinters.
  • Crystal System is monoclinic; 2/m
  • Crystal Habit is typically short prismatic crystals that have a psuedo-orthorhombic shape. The terminations are generally blunted with domes and minor pyramid faces. The crystals are striated lengthwise. Crystals are usually grouped into tight bundles and columnar, massive and fiberous forms are also known. Penetration and contact twinning does occassionally occur.
  • Cleavage is perfect in one direction lengthwise and good to fair in two other directions, one lengthwise at near right angles to the first one and one basal.
  • Fracture is uneven.
  • Hardness is 4
  • Specific Gravity is 4.3 (average for metallic minerals)
  • Streak is reddish to brownish black.
  • Associated Minerals are calcite, barite, garnets, limonite, siderite, pyrolusite and other manganese minerals.
  • Other Characteristics: Alters to pyrolusite which can coat the crystals, dulling the luster and can affect a streak test.
  • Notable Occurrences include Cornwall, England; Harz Mts., Germany; China; Sterling Hill, New Jersey and Negaunee, Michigan, USA and Ukraine.
  • Best Field Indicators are crystal habit, luster, striations, color and streak.




THE MARCASITE GROUP OF MINERALS
By Name
A list of minerals in alphabetical order
By Class
Elements, Oxides, Carbonates, etc.
Interesting Groupings
Gemstones, Birthstones, etc.
Physical Properties
Keys to identifying minerals
The Great Localities
Places that have made a name for themselves with mineral collectors

Full Text Search
Mineral identification by keyword searching
The Marcasite Group is composed of minerals with a similar orthorhombic structure and related chemistry. It is named for its most common member, marcasite. The general formula for this group is AX2. The A can be either iron, cobalt, nickel, osmium, iridium and/or ruthenium. The X can be either sulfur, arsenic, selenium and/or tellurium. Marcasite's formula is FeS2 for example. The members of the Lollingite Group are sometimes placed in the Marcasite Group. Marcasite is the only common member of this group.
The following are members of the Marcasite Group of minerals:
  • Anduoite (Ruthenium Osmium Arsenide)
  • Ferroselite (Iron Selenide)
  • Frohbergite (Iron Telluride)
  • Hastite (Cobalt Selenide)
  • Iridarsenite (Iridium Ruthenium Arsenide)
  • Kullerudite (Nickel Selenide)
  • Marcasite (Iron Sulfide)
  • Mattagamite (Cobalt Telluride)
  • Omeiite (Osmium Ruthenium Arsenide)
  • The Lollingite Group:
    • Costilbite (Cobalt Antimonide Sulfide)
    • Lollingite (Iron Arsenide)
    • Nisbite (Nickel Antimonide)
    • Rammelsbergite (Nickel Arsenide)
    • Safflorite (Cobalt Arsenide)
    • Seinajokite (Iron Nickel Antimonide Arsenide)


 

 

   

THE MINERAL MARCASITE

 


Marcasite, whose name is derived from the Arabic word for pyrite, is a common and an attractive mineral. The two minerals, marcasite and pyrite, are often confused due to their similar characteristics. Marcasite is a polymorph of pyrite which means that it has the same chemistry as pyrite but a different structure and, therefore, different symmetry and crystal shapes. The marcasite/pyrite polymorh pair is probably the most famous polymorph pair next to the diamond/graphite pair. Adding to the confusion between marcasite and pyrite is the use of the word marcasite as a jewelry trade name. The term is applied to small polished and faceted stones that are inlayed in sterling silver. But even though they are called marcasite, they are actually pyrite.

Marcasite is difficult to distinguish from pyrite when a lack of distinctive crystal habits exists. In fact, many specimens have been wrongly identified as pyrite or marcasite by even experienced mineral collectors. For many years the iron sulfide "Suns" found in Illinois coal mines were called "Marcasite Suns" (also known as "Marcasite Dollars") until X-ray studies showed them to be mostly pyrite. They have a habit that looks like marcasite. The possibility that they were originally marcasite and then later transformed into pyrite is being studied. Now they are correctly called "Pyrite Suns", but the confusion still exists. Many marcasite specimens are distinctive enough to reveal their true identity and make interesting and beautiful display specimens.

The most famous habit for marcasite is its "cock's comb" twinned habit. The crystals appear like a roster's head crest, hence the name. The habit is very distinctive and can not be mistaken for any other mineral.

Marcasite has been known to pseudomorph other minerals. A pseudomorph is an atom by atom replacement of one mineral's chemistry for another. If done subtly, the replacement can leave the old mineral's shape intact. The effect is one mineral in the shape of another, hence the term pseudomorph (Latin for false shape). Marcasite has pseudomorphed pyrite, gypsum, fluorite and others. At other times marcasite is pseudomorphed itself into the iron oxide mineral goethite. Often the replacement is only peripheral and leaves a thin skin of iron oxides on the crystals. These iron oxides are seen as an iridescence sheen and can provide marcasite specimens with quite an attractive and colorful appearance. These oxides may also have a positive effect in slowing marcasite's unfortunate deterioration.

Over a period of years, marcasite will oxidize in collections, freeing sulfur which forms sulfuric acid. The acid will then attack the paper label and even the cardboard box holding the specimen. Over a period of decades, most marcasite specimens will have disintegrated into an undesirable dust along with deteriorated paper scraps. A sulfur smell released during this reaction is often the easiest characteristic distinguishing Marcasite from Pyrite. The reaction is triggered by exposure to air and is an exothermic reaction, meaning that the reaction releases heat. This does not mean that marcasite hand specimens will feel warm to the touch, but in some marcasite rich portions of certain mines the mine walls would get too hot to touch because of this reaction. Ironically, specimens with iridescent oxide coatings have shown a resistance to deterioration and seem to survive longer than "fresh" maracasites. Either way marcasite is an interesting and attractive mineral and even with the slow deterioration can be a pleasure to own for many many years.

 

PHYSICAL CHARACTERISTICS:

  • Color is brassy yellow with a greenish tint at times. A multi-colored tarnish may exist that is the result of oxidation.
  • Luster is metallic.
  • Transparency: Crystals are opaque.
  • Crystal System is orthorhombic; 2/m 2/m 2/m
  • Crystal Habits include the tabular, bladed or prismatic forms. A twinning effect produces spear shaped crystal and repeated twinning produces a "cock's comb" cluster. Also massive, botryoidal, stalactitic and nodular. Sometimes as a replacement mineral of fossils and a pseudomorph of pyrite.
  • Cleavage is poor in two directions.
  • Fracture is uneven.
  • Hardness is 6 - 6.5
  • Specific Gravity is approximately 4.8+ (average for metallic minerals)
  • Streak is greenish to brownish black.
  • Other Characteristics: A sulfur smell is sometimes detectable.
  • Associated Minerals are calcite, dolomite, quartz, goethite, fluorite, pyrrhotite, bornite, chalcocite, sphalerite, pyrite, galena and other sulfides.
  • Notable Occurrences are widespread, but the more notable sites include Joplin, Missouri; Grant County, Wisconsin and Hardin County, Illinios, USA; Guanajuato, Mexico; Escale Pas de Calais, France; Peru; China and Russia.
  • Best Field Indicators are crystal habit, smell and greenish tint.



 

   

THE MINERAL MASSICOT

 


Massicot, which has been known by the chemically descriptive term of "lead monoxide", is an oxidation product of other lead minerals. It forms under oxidizing conditions of lead ore bodies and its presence is very indicative of the degree of oxidation. Something of interest to petrologists (rock scientists). It is probably more common than is known as it exists as a slight yellowish coating on many lead specimens, often to the detriment of the aesthetic appeal of the underlying mineral.

Massicot is the orthorhombic variety of PbO. The tetragonal variety is the mineral litharge. Both minerals have the same chemistry, PbO, but different structures. Because of this they are called dimorphs ("di" means two and "morph" means shape). Two other much more famous dimorphs are diamond and graphite; both of which are composed of carbon. Litharge is similar to the more common massicot, but the tetragonal structure is apparently lighter than massicot's orthorhombic structure. Litharge is also more orange in color. The two minerals are easily distinguished in petrographic microscopes due to optical differences. It has been found that many crystals of massicot have a fringe of litharge.

 

THE PHYSICAL CHARACTERISTICS OF MASSICOT:

  • Color is yellow to reddish yellow due to minium inclusions.
  • Luster is greasy, earthy to dull.
  • Transparency: Crystals are generally opaque, but thin scales can be transparent.
  • Crystal System is orthorhombic; 2 2 2.
  • Crystal Habits include massive, earthy and scaly coatings on other lead minerals.
  • Cleavage is distinct in two perpendicular directions, but is rarely seen.
  • Fracture is uneven.
  • Hardness is 2.
  • Specific Gravity is 9.6 - 9.7 (Well above average for any mineral)
  • Streak is light yellow.
  • Associated Minerals include minium, galena, barite, wulfenite, pyromorphite, mimetite, bindheimite, cerussite, lead and sphalerite.
  • Notable Occurrences include Freiberg, Saxony, Germany as well as in Inyo County, California; at the Dogwater Mine, Graham County; Tonopah-Belmont Mine, Maricopa County and Cababi District, Arizona; Potosi, Missouri and at Leadville, Colorado, USA; Sardinia, Italy; Mexico; Hungary; and at Lavrion, Greece.







 

MELANITE, THE BLACK VARIETY OF ANDRADITE GARNET

VARIETY INFORMATION:

  • VARIETY OF: Andradite garnet, Ca3 Fe2 Si3 O12.
  • USES: Gemstone.
  • COLOR: various shades of black.
  • INDEX OF REFRACTION: 1.89
  • HARDNESS: 6.5 - 7
  • CLEAVAGE: none
  • CRYSTAL SYSTEM: isometric
  • SPECIMENS

Melanite is one of the gem varieties of the garnet mineral, andradite. Its black color combined with the "garnet" shape is generally sufficient to identify melanite. Crystals are typically opaque, although some specimens with internal fractures will show highlights indicating a degree of translucence. Sometimes these highlights will be green or golden. The color is due to a high titanium content, and occasionally melanite is referred to as "titanian andradite".



 

THE MINERAL MELANOPHLOGITE

 

  • Chemistry: C2H17O5Si46O92 , Silicon Oxide with organic compounds.
  • Class: Organic Minerals
  • Uses: Only as mineral specimens.
  • Specimens

Melanophlogite, besides having a great name, is a very rare mineral being found in only a few sites. Some mineral purists might not agree that it is a mineral, as they tend to dislike any organic connection to minerals (see anapaite). In this example, not only is there a connection, but organic chemicals are obviously in the formula! Melanophlogite does form crystals, and attractive ones too; however, the actual symmetry is still in doubt. Individual crystals of melanophlogite appear cubic, but they could just be pseudo-cubic (see boleite). An examination of the formula for melanophlogite (C2H17O5Si46O92) reveals a large amount of SiO2 or silica. It might be tempting to conclude that it is just organically impure quartz, but melanophlogite isn't. If it were quartz, it would have quartz's structure and symmetry, and it definitely does not have these. As long as one can ignore the organic chemical connection, melanophlogite is its own mineral because it is naturally formed, a crystalline solid (repetitive), formed with no direct biological connection, and composed of a set chemical formula. The mineral whewellite, having a formula of CaC2O4 - H2O and being the salt of oxalic acid, has a similar problem.

 

PHYSICAL CHARACTERISTICS:

  • Color is colorless or white.
  • Luster is vitreous.
  • Transparency crystals are transparent to translucent.
  • Crystal System is tetragonal or possibly isometric.
  • Crystal Habits include botryoidal, globular clusters and cubes (if it is isometric, they are cubes; if tetragonal, they are pseudo-cubic crystals).
  • Cleavage is not present.
  • Fracture is conchoidal.
  • Hardness is 6.5 - 7.
  • Specific Gravity is 2.0+ (well below average)
  • Streak is white.
  • Associated Minerals include calcite, sulfur and other sedimentary minerals.
  • Notable Occurrences are limited to Giona Mine, Girgenti and other sites in Sicily, Italy.
  • Best Field Indicators are crystal habit, hardness, very low density and locality.

 

 

 

THE MINERAL MELANTERITE

 

  • Chemistry: FeSO4 - 7H2O, Hydrated Iron Sulfate.
  • Class: Sulfates
  • Group: Melanterite
  • Uses: A very minor ore of iron and as mineral specimens.
  • Specimens

Melanterite is one of only a few water soluble sulfate minerals. It forms in the near-surface secondary oxidation zone of ore deposits usually late in their development. In many mines, melanterite is an ongoing precipitate or efflorescent forming white to green encrustations, crystal aggregates and stalactites right on the sides of the mine's shafts. The primary source of the iron for melanterite is iron sulfides such as pyrite, pyrrhotite, marcasite and chalcopyrite.

A technique for removing copper from the copper sulfate mineral chalcanthite is responsible for the naming of an alternate name for melanterite. Chalcanthite, like melanterite, is soluble in water and it thus makes a solution of copper sulfate. If metallic iron is added to the solution, then metallic copper precipitates, leaving a solution of iron sulfate. This left-over solution has the same composition as a solution made from dissolving melanterite. The alternate name for melanterite is "copperas", from the Greek meaning "copper water", an allusion to the left-over solution. In a way, this could be thought of as "copper-providing water".

Attractive crystals of melanterite with a beautiful blue-green color are know to exist and are sought after. The shades toward blue come from impurities of copper which can substitute for as much as one third of the iron. The more copper, the bluer the crystals. Generally melanterite is known as having a white or green color.

Melanterite is also the name of a group of only five monoclinic sulfates of which melanterite is the only somewhat common member. Members of this group have the same basic structure as melanterite, but can have in place of iron, ions of manganese, zinc, cobalt and copper.
These are the members of the Melanterite Group:
  • Bieberite (Hydrated Cobalt Sulfate)
  • Boothite (Hydrated Copper Sulfate)
  • Mallardite (Hydrated Manganese Sulfate)
  • Melanterite (Hydrated Iron Sulfate)
  • Zinc-melanterite (Hydrated Zinc Copper Iron Sulfate)

 

PHYSICAL CHARACTERISTICS:

  • Color is white, green, yellowish green or blue-green.
  • Luster is vitreous to silky.
  • Transparency: Crystals are translucent to slightly transparent.
  • Crystal System is monoclinic; 2/m.
  • Crystal Habits include stubby prismatic or blocky to tabular crystals, sometimes as pseudo-octahedrons. Also acicular, fibrous and capillary and found as encrusting, stalactitic and concretionary masses.
  • Cleavage is perfect in one direct but only distinct in another.
  • Fracture is conchoidal.
  • Hardness is 2
  • Specific Gravity is approximately 1.9 (well below average).
  • Streak is white.
  • Other Characteristics: Is soluble in water and may deteriorate with absorption of water. The taste has a sweet, astringent and metallic character.
  • Associated Minerals are epsomite, chalcanthite, gypsum, pyrite, pyrrhotite, marcasite and chalcopyrite.
  • Notable Occurrences include Minas de Rio Tinto, Spain; Rammelsberg, Harz Mountains, Germany and Falun, Sweden; and in the United States at Ducktown, Tennessee; South Dakota; Colorado; Bigham Canyon, Utah; Comstock Lode, Lincoln County, Nevada; Butte, Montana; at several mines in Arizona and at The Geysers in Sonoma County and at Leona Heights, Alameda County, California.
  • Best Field Indicators are crystal habit, low density, associations, solubility in water, taste and color.

 

 

THE MINERAL MENEGHINITE

 

  • Chemistry: Pb13Sb7S23, Lead Antimony Sulfide
  • Class: Sulfides
  • Subclass: Sulfosalts
  • Uses: Mineral specimens and as a very minor ore of lead.
  • Specimens

Meneghinite is a rare mineral that generally forms interesting acicular crystals. Meneghinite is one of several lead antimony sulfides. The elements lead, antimony and sulfur have the capability of forming many different minerals. There are at least a dozen different minerals with just lead, antimony and sulfur comprising their chemistries. All of those minerals are sulfosalts, a segment of sulfides where the antimony acts more like a metal than a non-metal and occupies a position where it is bonded to sulfurs. They have some very similar properties such as a gray color, high density, low hardness, metallic luster, dark gray to black streaks and a similar environment of formation. Most form from hydrothermal fluids that crystallize at lower temperatures than other sulfides. They can be distinguish only by differences in their respective crystal habits, cleavages, fracture and x-ray techniques. The table below shows most of the lead antimony sulfides and their formulas (some have additional elements).


MINERAL
FORMULA
MINERAL
FORMULA
MINERAL
FORMULA
ANDORITE
PbAgSb3S6
BOULANGERITE
Pb5Sb4S11
FREIESLEBENITE
PbAgSbS3
FULOPPITE
Pb3Sb8S15
GEOCRONITE
Pb14(Sb, As)6S23
GUETTARDITE
Pb(Sb, As)2S4
HETEROMORPHITE
Pb7Sb8S19
JAMSONITE
Pb13FeSb7S23
LAUNAYITE
Pb22Sb26S61
MENEGHINITE
Pb13Sb7S23
PARAJAMSONITE
Pb4FeSb7S23
PLAGIONITE
Pb5Sb8S17
PLAYFAIRITE
Pb16Sb18S43
ROBINSONITE
Pb4Sb6S13
SEMSEYITE
Pb9Sb8S21
SORBYITE
Pb19(Sb, As)20S49
TWINNITE
Pb(Sb, As)2S4
ZINKENITE
Pb9Sb22S42

 

 

PHYSICAL CHARACTERISTICS OF MENEGHINITE:

  • Color is lead gray to black.
  • Luster is metallic.
  • Transparency: Crystals are opaque.
  • Crystal System: Orthorhombic: 2/m 2/m 2/m.
  • Crystal Habits include common acicular to prismatic, granular and even some fibrous crystals and massive forms.
  • Cleavage is perfect in one direction (prismatic).
  • Hardness is 2.5
  • Specific Gravity is 6.3 - 6.4 (heavier than average for metallic minerals)
  • Streak is steel gray.
  • Associated Minerals include calcite, galena, sphalerite, tetrahedrite, arsenopyrite and several other sulfosalts.
  • Notable Occurrences include the type locality of Bottino Mine, Serravezza, Alpe Apuane, Toscana, Italy as well as Chamonix Valley, France; Turkey; Kalkar Quarry, Santa Cruz County, California, USA and Marble Lake, Frontenac County, Ontario, Canada.
  • Best Field Indicators are crystal habit, associations, cleavage, locality and density.






 

             

NATIVE MERCURY

 

  • Chemistry: Hg, Elemental Mercury
  • Class: Elements
  • Group: Gold
  • Uses: Minor ore of mercury, electrical switches, thermometers
  • Specimens

Mercury is unique, as it is the only metal that is liquid at room temperature, having a melting point of -40 C, and a boiling point of 357 C. This silvery liquid metal is very dense, yet has a high surface tension that causes is to form tiny little perfect spheres in the pores of the rocks it is found in. Many mineralogical characteristics simply do not apply to a liquid: there is no "hardness", since it cannot be scratched (nor can it scratch); there is no crystal structure, no fracture, no cleavage, no streak; all of course, at room temperatures. When frozen, mercury forms crystals in the rhombohedral system at low pressure, and in the tetragonal system at high pressure.

 

PHYSICAL CHARACTERISTICS:

  • Color is bright silvery metalic.
  • Luster is metallic.
  • Transparency is opaque.
  • Crystal System does not apply
  • Crystal Habits spherical droplets, or pools of mercury liquid.
  • Cleavage does not apply
  • Fracture does not apply
  • Streak does not apply
  • Hardness does not apply
  • Specific Gravity is 13.5+ (very dense)
  • Associated Minerals are cinnabar, calomel, and other secondary mercury minerals.
  • Other Characteristics: Mercury is a liquid! It also expans at a constant rate with a rise in temperature.
  • Notable Occurrences include Almaden, Spain; Idrija, former Yugoslavia; Italy; California, Oregon, Texas, and Arkansas, USA.
  • Best Field Indicators its a liquid!



 

  

 THE MINERAL MESOLITE

 


Mesolite is a popular zeolite mineral for mineral collectors and zeolite collectors in particular. Its radiating sprays of ice-clear acicular crystals are a hallmark of this mineral. Often associated with minerals such as the green or clear apophyllite, the pink and pearly heulandite and the sparkling tiny crystals of quartz, mesolite is a wonderful addition in both style and rarity to these great mineral assemblages.

Mesolite's structure has a typical zeolite openness about it that allows large ions and molecules to reside and actually move around inside the overall framework. The structure contains open channels that allow water and large ions to travel into and out of the crystal structure. The size of these channels controls the size of the molecules or ions and therefore a zeolite like mesolite can act as a chemical sieve. Mesolite's structure contains chains of silicate tetrahedrons aligned in one direction and this produces the needle-like crystals and the cleavage results from the weaker bonds between the chains.

Mesolite, a sodium calcium zeolite, is intermediate between natrolite, a sodium zeolite, and scolecite, a calcium zeolite. They are closely related and sometimes found together. The presence of calcium in two of the minerals slightly alters the structure from that of natrolite from an orthorhombic symmetry to a monoclinic symmetry. Although twinning of scolecite and mesolite often make them look orthorhombic The three minerals are referred to as "chain" or "needle" zeolites. They are similar and hard to distinguish when in clusters with radiating, acicular habits. Natrolite forms thinner crystals with pyramidal terminations, and mesolite's fiber-like crystals are usually the thinnest crystals of the three minerals. Scolecite's larger crystals tend to be more robust and durable. These characteristics are only generalities and can not be used as dependable identifying traits. Absolute identification can not be made by ordinary means.

 

 

PHYSICAL CHARACTERISTICS:

  • Color is clear or white.
  • Luster is vitreous.
  • Transparency: crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include sprays of needle thin acicular crystals with a slanted domal termination. Also nodules, fibrous and earthy masses.
  • Cleavage is perfect in two directions, prismatic. Cleavage is rarely seen due to small crystal size.
  • Fracture is conchoidal to uneven.
  • Hardness is 5 - 5.5.
  • Specific Gravity is approximately 2.2 - 2.4 (very light)
  • Streak is white.
  • Other Characteristics: Masses can have a chatoyant (cat's eye) effect.
  • Associated Minerals are quartz, apophyllite, datolite, heulandite, stilbite and other zeolites.
  • Notable Occurrences include Poona, India; Giants Causeway, Ireland; Skye, Scotland; Colorado, New Jersey and Oregon, USA and Berufjord, Iceland.
  • Best Field Indicators are crystal habit, density and associations.



 

THE MINERAL META-ANKOLEITE

 

  • Chemistry: KUO2PO4 - 3H2O, Hydrated Potassium Uranyl Phosphate
  • Class: Phosphates
  • Group: Meta-autunite
  • Uses: A very minor ore of uranium and as mineral specimens.
  • Specimens

Meta-ankoleite was thought to be a dehydration product of the mineral, ankoleite, hence the name. Ankoleite is no longer recognized as a mineral or never was really established, but in any case it leaves meta-ankoleite without a corresponding non-meta-mineral. Meta is Latin for changed as in changed-ankoleite. This prefix is used when minerals have slightly altered from one mineral to another by natural processes and the mineralogist whom identifies the new mineral feels that the meta prefix would be appropriate. In this case as in the case of many of the other members of the Meta-autunite Group, the change occurs with the dehydration of the original mineral into a new mineral. Often the loss of a water molecule or two is not significant, but in these phosphate minerals it has been found to be telling. However with meta-ankoleite it is the original mineral so its name is somewhat of a misnomer. It is still placed in the Meta-autunite Group because of its structural similarities to these other minerals.

The structure of meta-ankoleite is composed of flattened phosphate tetrahedrons linked to uranium-oxygen groups that form distorted octagons. The phosphate and uranium groups form sheets that are weakly held together by water molecules. This structure produces the tabular habit, the one perfect direction of cleavage, and the relative softness. It is an analogous structure to that of the phyllosilicates. The flattened tetrahedrons have a near four fold symmetry and the distorted octagons contribute to the tetragonal symmetry.

Meta-ankoleite is one of several fluorescent minerals from the fluorescent mineral capital of the world at Sterling Hill, New Jersey, USA. It fluoresces a green color there under shortwave ultraviolet light. At meta-ankoleite's type locality in the Ankole District, Uganda specimens fluoresce a yellow-green color under both shortwave and longwave radiation. Remember, this is a radioactive mineral and should be stored away from other minerals that are affected by radioactivity and human exposure should always be limited.

 

 

 

 

PHYSICAL CHARACTERISTICS:

  • Color is yellow.
  • Luster is vitreous to dull.
  • Transparency: Crystals are translucent to transparent.
  • Crystal System is tetragonal; 4/m 2/m 2/m.
  • Crystal Habits include platy square crystals. Also as crusts, micaceous, foliated and earthy.
  • Cleavage is perfect in one direction.
  • Fracture is uneven.
  • Hardness is 2 - 2.5
  • Specific Gravity is approximately 3.5 (above average for translucent minerals).
  • Streak is a pale yellow.
  • Other Characteristics: Radioactive and fluorescent yellow-green or green.
  • Associated Minerals include quartz, muscovite, phosphuranylite and uranium minerals.
  • Notable Occurrences include the type locality of Mungenyi Pegmatite, Ankole District (hence the name), Uganda and at Sterling Hill, New Jersey, USA.
  • Best Field Indicators are color, crystal habit, fluorescence, radioactivity, associations, cleavage and brittle cleavage sheets.



 

 

THE MINERAL META-AUTUNITE

 

  • Chemistry: Ca(UO2)2(PO4)2 - 2-6H2O, Hydrated Calcium Uranyl Phosphate
  • Class: Phosphates
  • Group: Meta-autunite
  • Uses: A minor ore of uranium and as mineral specimens.
  • Specimens

Meta-autunite is a dehydration product of its close cousin, autunite, hence the name. When the mineral autunite loses water and converts to meta-autunite, it becomes what is known as a pseudomorph. A pseudomorph is generally an atom by atom replacement of one mineral's chemistry in place of another mineral's chemistry, while the original crystal's outward shape remains largely unchanged. The process leaves the crystal shape of the original mineral intact, but the original mineral is no longer there. Pseudomorph translated from latin means false shape (pseudo=false; morph=shape).

In this case, the conversion is not so dramatic since it involves only the loss of a few water molecules; therefore, a good pseudomorph is likely. The conversion from autunite to meta-autunite is reversible with addition of water, unlike most other examples from the Meta-autunite Group. In a way, meta-autunite and autunite are similar to zeolites in their hydration/dehydration capabilities. Meta-autunite can be found in nature, possibly formed without going through the autunite phase. Meta-autunite is the more stable form of the two and most specimens of autunite are probably meta-autunite, if the truth be told.

The structure of meta-autunite is composed of phosphate tetrahedrons linked to uranium-oxygen groups that form distorted octahedrons. The phosphate and uranium groups form sheets that are weakly held together by water molecules. This structure produces the tabular habit, the one perfect direction of cleavage, and the relative softness. It is an analogous structure to that of the phyllosilicates.

Meta-autunite is a highly fluorescent mineral. It is said to fluoresce with a brightness comparable to some of the brightest fluorescing minerals in the world. The bright green fluorescence of meta-autunite is similar to other green fluorescing minerals such as autunite, adamite, green fluorescing opal and of course the spectacular willemites from Franklin, New Jersey, USA. The uranium is the fluorescent activator in meta-autunite and autunite. Trace amounts of uranium are responsible for the green fluorescence in opal and adamite as well. Remember because of the uranium, meta-autunite is a radioactive mineral and should be stored away from other minerals that are affected by radioactivity and human exposure should always be limited.

 

 

 

 

 

 

PHYSICAL CHARACTERISTICS:

  • Colors include lemon-yellow, greenish yellow to canary yellow (sometimes with a black core, possibly due to uraninite).
  • Luster is vitreous or pearly to dull.
  • Transparency: Crystals are translucent to opaque.
  • Crystal System is tetragonal; 4/m 2/m 2/m.
  • Crystal Habits include tabular square crystals dominated by two pinacoid faces. Crystals can look cubic (pseudocubic) too. Also as crusts, micaceous, foliated and earthy. Many crystals are pseudomorphs of autunite.
  • Cleavage is perfect in one direction.
  • Fracture is uneven.
  • Hardness is 2 - 2.5
  • Specific Gravity is approximately 3.5 - 3.6 (above average for translucent minerals and higher than autunite {3.1- 3.2} due to loss of water molecules).
  • Streak is a pale yellow.
  • Other Characteristics: Brightly fluorescent green to yellow-green, radioactive and cleavage sheets are surprisingly brittle.
  • Associated Minerals include limonite, quartz, pyrite, meta-uranocircite, uranophane, meta-torbernite, autunite, torbernite, uranocircite, uraninite and other uranium minerals.
  • Notable Occurrences include the Dripping Springs Quartzite in Gila County , Arizona; the Daybreak Mine, Washington and the Miracle Mine and other localities in Kern County, California, USA; St. Austell and Redruth, Cornwall, England; Saxony, Germany and Rum Jungle, Australia.
  • Best Field Indicators are color, crystal habit, higher density than autunite, fluorescence, radioactivity, associations and cleavage.



 

THE MINERAL META-TORBERNITE

 


Meta-torbernite is a dehydration product of its close cousin, torbernite, hence the name. When the mineral torbernite loses water and converts to meta-torbernite, it usually undergoes pseudomorphism. A pseudomorph is generally an atom by atom replacement of one mineral's chemistry to form another mineral. The process leaves the crystal shape of the original mineral intact. Pseudomorph means false (pseudo) shape (morph). In this case, the conversion is not so dramatic since it involves only the loss of a few water molecules; therefore, a good pseudomorph is likely. The conversion is irreversible and ongoing, and all collection specimens of a certain age are almost certainly partially to totally converted. If accuracy is demanded, all torbernite collection pieces of a few years of age should be labeled as meta-torbenite.

The structure of meta-torbernite is composed of phosphate tetrahedrons linked to uranium-oxygen groups that form distorted octahedrons. The phosphates and uranium groups lie in sheets that are weakly held together by water molecules. This structure produces the tabular habit, the one perfect direction of cleavage, and the relative softness.

Remember, this is a radioactive mineral and should be stored away from other minerals that are affected by radioactivity and human exposure should always be limited.

 

PHYSICAL CHARACTERISTICS:

  • Colors are various shades of pale to dark green to almost black.
  • Luster is vitreous to dull.
  • Transparency crystals are translucent to opaque.
  • Crystal System is tetragonal; 4/m 2/m 2/m
  • Crystal Habits include tabular square crystals dominated by two pinacoid faces. Crystals can form in parallel growths giving a "stacked book" kind of look. Also as crusts, micaceous, foliated and scaly aggregates. Almost all meta-torbernite crystals are pseudomorphs of torbernite.
  • Cleavage is perfect in one direction.
  • Fracture is uneven.
  • Hardness is 2.5
  • Specific Gravity is approximately 3.7 (above average for translucent minerals)
  • Streak is a pale green.
  • Associated Minerals are autunite, uranophane, uranocircite, torbernite, uraninite and other uranium minerals.
  • Other Characteristics: radioactive, and cleavage sheets are surprisingly brittle.
  • Notable Occurences include Cornwall, England; Athabasca, Saskatchewan, Canada; Shaba, Zaire; Saxony, Germany and France.
  • Best Field Indicators are color, crystal habit, non-fluorescence, higher density than torbernite, radioactivity, associations, and brittle cleavage sheets.



 

THE MINERAL META-URANOCIRCITE

 

  • Chemistry: Ba(UO2)2(PO4)2 - 6-8H2O, Hydrated Barium Uranyl Phosphate
  • Class: Phosphates
  • Group: Meta-autunite
  • Uses: A minor ore of uranium and as mineral specimens.
  • Specimens

Meta-uranocircite is a dehydration product of its close cousin, uranocircite, hence the name. When the mineral uranocircite loses water and converts to meta-uranocircite, it becomes what is known as a pseudomorph. A pseudomorph is generally an atom by atom replacement of one mineral's chemistry in place of another mineral's chemistry, while the original crystal's outward shape remains largely unchanged. The process leaves the crystal shape of the original mineral intact, but the original mineral is no longer there. Pseudomorph translated means false shape (pseudo=false; morph=shape).

In this case, the conversion is not so dramatic since it involves only the loss of a few water molecules; therefore, a good pseudomorph is likely. The conversion from uranocircite to meta-uranocircite is irreversible and ongoing, and all collection specimens of a certain age are almost certainly partially to totally converted. If accuracy is demanded, all uranocircite collection pieces of a few years of age or more should be labeled as meta-uranocircite. Meta-uranocircite can be found naturally in nature, but these specimens probably started out as uranocircite.

The structure of meta-uranocircite is composed of phosphate tetrahedrons linked to uranium-oxygen groups that form distorted octahedrons. The phosphate and uranium groups form sheets that are weakly held together by water molecules. This structure produces the tabular habit, the one perfect direction of cleavage, and the relative softness. It is an analogous structure to that of the phyllosilicates. Its symmetry is monoclinic although it outwardly appears to be tetragonal (i.e. pseudotetragonal).

Remember, this is a radioactive mineral and should be stored away from other minerals that are affected by radioactivity and human exposure should always be limited.

 

PHYSICAL CHARACTERISTICS:

  • Colors include yellow to yellow-green.
  • Luster is vitreous or pearly to dull.
  • Transparency: Crystals are translucent to opaque.
  • Crystal System is monoclinic (pseudotetragonal).
  • Crystal Habits include tabular square crystals dominated by two pinacoid faces. Crystals can look cubic (pseudocubic) too. Also as crusts, micaceous, foliated and earthy. Almost all meta-uranocircite crystals are pseudomorphs of uranocircite.
  • Cleavage is perfect in one direction.
  • Fracture is uneven.
  • Hardness is 2 - 2.5
  • Specific Gravity is approximately 4.1 (well above average for translucent minerals and higher than uranocircite due to loss of water molecules).
  • Streak is a pale yellow.
  • Other Characteristics: Radioactive, fluorescent green and cleavage sheets are surprisingly brittle.
  • Associated Minerals include limonite, quartz, meta-autunite, meta-torbernite, autunite, torbernite, uranocircite, uraninite and other uranium minerals. Some meta-uranocircite is found in petrified wood in Arizona.
  • Notable Occurrences include the Cameron area of Coconino County and Dripping Springs Quartzite in Gila County , Arizona; Kern County, California and Harding County, South Dakota, USA; Bergen, Saxony, Germany; Banat, Romania and Antsirabe, Madagascar.
  • Best Field Indicators are color, crystal habit, fluorescence, higher density than uranocircite, radioactivity, associations, cleavage and brittle cleavage sheets.



 

 

THE MINERAL META-VARISCITE

 

  • Chemistry: AlPO4 - 2H2O, Hydrated Aluminum Phosphate
  • Class: Phosphates
  • Uses: Only as mineral specimens.
  • Specimens

Metavariscite is a rare phosphate mineral that is rather difficult to distinguish from its very close cousin, variscite. The two minerals are polymorphs, meaning many shapes, since the two minerals have the same chemistry but different atomic structures. Variscite is orthorhombic and metavariscite is monoclinic. Despite this difference the two are not easily distinguished as they rarely form even tiny crystals which might show their true symmetries. Both minerals form mostly crusts and nodules that are usually green. Metavariscite is almost always a pale green while variscite's color is somewhat more variable and when green is usually darker.

 

PHYSICAL CHARACTERISTICS:

  • Color is light green.
  • Luster is vitreous or waxy.
  • Transparency: Specimens are translucent to opaque.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include nodules, fine grain masses, and crusts.
  • Cleavage is not seen.
  • Fracture is conchoidal, splintery, uneven.
  • Hardness is variable from 3.5
  • Specific Gravity is approximately 2.53 (average)
  • Streak is white.
  • Associated Minerals are limonite, chalcedony, crandallite, variscite, wardite and other secondary phosphate minerals.
  • Notable Occurrence includes Edison-Bird Mine, Utah, USA.
  • Best Field Indicators are color, habit, associations, density and luster.



 

THE MINERAL META-ZEUNERITE

 


Meta-zeunerite is a dehydration product of its close cousin, zeunerite, hence the name. When the mineral zeunerite loses water and converts to meta-zeunerite, it becomes a pseudomorph. A pseudomorph is generally an atom by atom replacement of one mineral's chemistry in place of another mineral's chemistry, while the crystal's outward shape remains largely unchanged. The process leaves the crystal shape of the original mineral intact, but the original mineral is not there. Pseudomorph translated means false shape (pseudo=false; morph=shape).

In this case, the conversion is not so dramatic since it involves only the loss of a few water molecules; therefore, a good pseudomorph is likely. The conversion is irreversible and ongoing, and all collection specimens of a certain age are almost certainly partially to totally converted. If accuracy is demanded, all zeunerite collection pieces of a few years of age or more should be labeled as meta-zeunerite. Meta-zeunerite can be found naturally in nature, but probably started out as zeunerite.

The structure of meta-zeunerite is composed of arsenate tetrahedrons linked to uranium-oxygen groups that form distorted octahedrons. The arsenates and uranium groups form sheets that are weakly held together by water molecules. This structure produces the tabular habit, the one perfect direction of cleavage, and the relative softness. It is an analogous structure to that of the phyllosilicates.

Remember, this is a radioactive mineral and should be stored away from other minerals that are affected by radioactivity and human exposure should always be limited.

 

PHYSICAL CHARACTERISTICS:

  • Colors vary from pale to dark green.
  • Luster is vitreous to dull.
  • Transparency: Crystals are translucent to opaque.
  • Crystal System is tetragonal.
  • Crystal Habits include tabular square crystals dominated by two pinacoid faces. Bipyramidal crystals are also seen. Crystals can look cubic (pseudocubic) too. Also as crusts, micaceous, foliated and earthy. Almost all meta-zeunerite crystals are pseudomorphs of zeunerite.
  • Cleavage is perfect in one direction.
  • Fracture is uneven.
  • Hardness is 2.5
  • Specific Gravity is approximately 3.85 (above average for translucent minerals and higher than zeunerite due to loss of water molecules).
  • Streak is a pale green.
  • Other Characteristics: Radioactive, non-fluorescent and cleavage sheets are surprisingly brittle.
  • Associated Minerals are barite, fluorite, quartz, limonite, olivenite, brochantite, scorodite, meta-autunite, meta-torbernite, heinrichite, uraninite and other uranium minerals.
  • Notable Occurrences include Centennial Eureka Mine, Tintic, Utah; the Kern River uranium deposits in Kern County and near Crystal Peak in Plumas County, California and the Grandview Mine and other unanium localities in Arizona, USA; Weisser Hirsch Mine, Schneeberg, Saxony, Germany; Wheal Edward Mine, Cornwall, England and other localities with uranium arsenic minerals.
  • Best Field Indicators are color, crystal habit, non-fluorescence, higher density than zeunerite, radioactivity, associations, cleavage and brittle cleavage sheets.




  

THE MINERAL MIARGYRITE

 

  • Chemistry: AgSbS2, Silver Antimony Sulfide
  • Class: Sulfides
  • Subclass: Sulfosalts
  • Uses: Mineral specimens and as a minor ore of silver.
  • Specimens

Miargyrite is a another interesting silver sulfide mineral that is popular with collectors who love to collect silver bearing minerals. Other silver sulfide minerals include stephanite, pyrargyrite, polybasite, proustite, argyrodite, andorite and acanthite among many others. It is easy to confuse miargyrite with some of these other minerals, but its crystal habit and unusual streak will generally suffice to differentiate it. Miargyrite is a sulfosalt, a segment of sulfides where the antimony acts more like a metal than a non-metal and occupies a position where it is bonded to sulfurs.

 

PHYSICAL CHARACTERISTICS:

  • Color is iron black to steel gray.
  • Luster is metallic.
  • Transparency: Crystals are opaque.
  • Crystal System: Monoclinic; 2/m.
  • Crystal Habits include complex crystals with a tabular character and massive.
  • Cleavage: Not discernible.
  • Fracture: Conchoidal.
  • Hardness is 2 - 2.5
  • Specific Gravity is 5.1 - 5.3 (somewhat heavier than average for metallic minerals)
  • Streak is cherry-red.
  • Other Characteristics: Specimens will darken with exposure to light.
  • Associated Minerals include pyrargyrite, polybasite, proustite, galena, chalcopyrite and acanthite.
  • Notable Occurrences include Saxony and the Harz Mountains of Germany; Pribram, Czech Republic; San Juan, Colorado; Silver City, Idaho; Cerbat Mountains, Arizona and California, USA; Romania; Chile and Bolivia.
  • Best Field Indicators are crystal habit, streak, softness, color and luster.







   

THE MINERAL MICROCLINE

 

  • Chemistry: KAlSi3 O8 , Potassium aluminum silicate.
  • Class: Silicates
  • Subclass: Tectosilicates
  • Group: Feldspars
  • Uses: ornamental stone, in the manufacture of glass, enamel and porcelain products and as mineral specimens.
  • Specimens

Microcline is a common, but not a well known mineral and has been used as a semi-precious stone under the names of Amazonite and Perthite. Amazonite is a variety that is deep green and is suitable for carving and polishing. The perthite variety is a stripped, veined or almost zebra patterened stone, that is produced from lamellar intergrowths inside the crystal. These intergrowths result from compatible chemistries at high temperatures becoming incompatible at lower temperatures and thus a seperating and layering of these two phases. The colored stripes are microcline and the white or clear stripes are plagioclase feldspars. If there is more plagioclase than microcline it is called "antiperthite".

Microcline is a polymorph of other minerals that share the same chemistry but have different crystal structures. If positive identification can not be made by field methods then the specimen may be refered to as a potassium feldspar or K-spar. The other k-spar minerals are sanidine, orthoclase and anorthoclase. The differences between these minerals are minor in hand samples but microcline tends to be deeper colored, is usually striated on cleavage planes and is the only one that can be, but is not always, a deep green (amazonite).

Twinning is common in all feldspars and follow certain twin laws such as the Albite Law, the Pericline Law, the Carlsbad Law, the Manebach Law and the Baveno Law. Albite and pericline Law type twinning produce stacks of twin layers that are typically only fractions of millimeters to several millimeters thick. These twinned layers can be seen as striation like grooves on the surface of the crystal and unlike true striations these also appear on the cleavage surfaces. Albite and pericline twinning is more common in plagioclase feldspars than with microcline. The Carlsbad Law twin produces what appears to be two intergrown crystals growing in opposite directions. Two different twin laws, the Manebach and Baveno laws, produce crystals with one prominant mirror plane and penetrant angles or notches into the crystal. Single crystals showing a perfect twin are rare and are often collected by twin fanciers.

Well formed crystals can be quite striking in appearance. At some localities fine amazonite clusters are intermixed with smoky quartz crystals and this results in an outstanding classic mineral specimen.

 

PHYSICAL CHARACTERISTICS:

  • Color is usually off-white,yellowish, flesh pink, brown or green.
  • Luster is vitreous to sometimes pearly or dull if weathered.
  • Transparency crystals are translucent, but usually translucent to opaque.
  • Crystal System is triclinic; bar 1
  • Crystal Habits include blocky, or tabular crystals. Crystals have a nearly rectangular or square cross-section with slightly slanted dome and pinacoid terminations. Twinning is common. Crystals can be twinned according to the Albite, Pericline, Carlsbad, Manebach and Baveno laws. Microcline can be found as a major rock forming component in granites, syenites and in metamorphic gneisses.
  • Cleavage is perfect in one and good in another direction forming nearly right angled prisms.
  • Fracture is conchoidal.
  • Hardness is 6 - 6.5.
  • Specific Gravity is approximately 2.5 (average)
  • Streak is white.
  • Associated Minerals are quartz, muscovite and plagioclase feldspars.
  • Other Characteristics: Lamellar twinning may cause a grooved effect on cystal and cleavage surfaces that appear as striations. Perthite intergrowths causes a stripped appearance is some specimens.
  • Notable Occurrences include Pikes Peak region of Colorado and North Carolina among other sites in the USA; Russia; Norway and Madagascar.
  • Best Field Indicators are occurence, twinning, color and luster.

 

  

THE MINERAL MICROLITE

 

  • Chemical Formula: (Ca, Na)2Ta2O6(O, OH, F); Calcium Sodium Tantalum Oxide Hydroxide Fluoride.
  • Class: Oxides and Hydroxides
  • Group: Pyrochlore
  • Uses: A very minor ore of tantalum, as mineral specimens and sometimes cut as a gemstone.
  • Specimens

Microlite is one of the tantalum/niobium oxides that are generally difficult to distinguish. Fortunately there are few of them that form well shaped octahedral crystals. Microlite crystallizes in the isometric symmetry class and forms fine octahedral crystals that are typically and characteristically modified by other isometric forms. Other members of the Pyrochlore Group also form octahedrons, but can sometimes be reliably differentiated by color, streak and other characteristics.

Microlite generally contains impurities of radioactive elements called rare earths and this produces the slight radioactivity in this mineral. It is occasionally placed in the informal group of minerals called the Rare Earth Oxides, but does not contain a significant amount of these metals.

Microlite is an end member of a solid-solution series between itself and the mineral pyrochlore from where the Pyrochlore Group gets its name. The two minerals have similar structures and properties, but microlite is the tantalum rich end member and pyrochlore is the niobium rich end member. Microlite is found mostly in granitic pegmatite dikes and more rarely in calcite rich rocks called carbonatites. The rarer pyrochlore on the other hand is more common to the carbonatites and alkalic pegmatites called nepheline syenites.

The mineral gahnite also forms octahedrons but is neither a rare earth mineral nor apart of the pyrochlore Group of minerals. Gahnite is a member of the Spinel Group of oxide minerals. Its green color makes it easy to confuse with the green varieties of microlite, but microlite is generally denser and much softer.

Remember, this is a slightly radioactive mineral and should be stored away from other minerals that are subject to damage from radioactivity and of course human exposure should be limited !

 

PHYSICAL CHARACTERISTICS:

  • Color is pale yellow, reddish-brown, red, olive or even emerald green.
  • Luster is vitreous to resinous.
  • Transparency: Crystals are generally translucent with darker specimens being opaque.
  • Crystal System is isometric; 4/m bar 3 2/m
  • Crystal Habits typically include octahedral crystals that are modified by other isometric forms; also found granular as disseminated grains and massive. Although the name microlite was applied to the mineral for the tiny crystals that were first found, larger crystals up to 2 cm have been found.
  • Cleavage is in four directions (octahedral), but is indistinct.
  • Fracture is subconchoidal to uneven.
  • Hardness is 5 - 5.5
  • Specific Gravity is approximately 4.3 - 5.7 (heavy for non-metallic). Variation caused by extent of inclusion of trace metals into the structure.
  • Streak is white or pale yellow to brown.
  • Other Characteristics: Slightly radioactive.
  • Associated Minerals include quartz, feldspars, calcite, columbite, tantalite, zircon, biotite, lepidolite, spodumene and simpsonite.
  • Notable Occurrences include Virgem da Lapa region of Minas Gerais, Brazil; Iveland, Norway; Verutrask, Sweden; Greenland; Wodinga, Australia; Madagascar and Amelia Courthouse, Virginia; Black Hills, South Dakota; Dixon, New Mexico; California; Colorado and many of the rare earth pegmatites of New England, USA.
  • Best Field Indicators are crystal habit, luster, fracture, color, hardness, radioactivity, associations, environment and specific gravity.


    

THE MINERAL MILARITE

 


Milarite is a fairly rare mineral and yet it is one of the two minerals that gives its name to a somewhat large group of silicates, namely the Milarite - Osumilite Group. The group is composed of similar cyclosilicate minerals that are all very rare and very obscure with the exception of milarite, osumilite and sugilite. The primary structural unit of the minerals in the Milarite - Osumilite Group is a most unusual double ring, Si12O30. Normal rings of cyclosilicates are composed of six silicate tetrahedrons; Si6O18. The double rings of the Milarite - Osumilite Group minerals are made of two normal rings linked together by sharing one oxygen in each of the tetrahedrons. The structure is analogous to the dual wheels of a tractor trailer.

Milarite crystals are generally small, but can make excellent micromounted specimens. They are often colored a muted green or yellow and form good prismatic hexagonal crystals. Milarite forms as a primary mineral in granitic pegmatites and syenites, hydrothermal veins and alpine clefts. It has been cut as a gem, but is too rare, small and its general translucency that makes it only suitable to be cut for collectors of rare gemstones. Milarite is named for its locality of first discovery; Val Giuf (Val Milar), Tavetsch, Grischum, Switzerland. Milarite has been known as giufite and giuffite, but milarite is the only accepted name now. Good mineral specimens are available and can be quite attractive, but mostly under magnification.

 

PHYSICAL CHARACTERISTICS:

  • Color is colorless, white, pale green or yellow.
  • Luster is vitreous to dull.
  • Transparency: Crystals are translucent to transparent.
  • Crystal System is hexagonal; 6/m 2/m 2/m.
  • Crystal Habits include prismatic crystals with a pinacoidal termination.
  • Cleavage is poor in one direction.
  • Fracture is subconchoidal.
  • Hardness is 5.5 - 6
  • Specific Gravity is approximately 2.5 - 2.6 (average)
  • Streak is white.
  • Other Characteristics: Some specimens are fluorescent.
  • Notable Occurrences include the type locality of Val Giuf (Val Milar), Tavetsch, Grischum, Switzerland as well as Jaguaracu, Minas Gerais, Brazil; Valencia Mine, Guananajuato, Mexico; Henneberg, Germany; Kola Peninsula, Russia; Mont Saint-Hilaire, Quebec, Canada; Monte Cervandone, Piemonte, Italy; Langesunsfjord, Norway and Maehren, Czech Republic.
  • Best Field Indicators are hardness, color, luster and locality.



     

THE MINERAL MILLERITE

 

Millerite is one of a few sulfide minerals that form fine acicular crystals that appear as hair-like fibers aggregated into sprays. Boulangerite and jamesonite are two other sulfides that form similar acicular crystals. However, jamesonite is gray and brittle and boulangerite has flexible crystals.

The oxide rutile and the silicate elbaite, a tourmaline, are two other minerals that can be mistaken for millerite when they form acicular sprays of crystals. Millerite's environments of formation, mainly in hydrothermal replacement deposits and in limestone and dolomite cavities and associated geodes, usually serve as the best way to distinguish it from the aforementioned minerals.

It is a real bonus to quartz geode collectors from Indiana to Kansas to open up a geode and find a spray of brassy millerite crystals tucked inside. It is postulated that the source of the nickel for the millerite that is found in these geodes is somehow derived from a meteoritic origin. Perhaps nickel, dissolved from iron-nickel meteorites, leached into the geodes by way of ground water and found an environment suitable for the formation of millerite crystals. Speaking of meteorites, millerite is one of several minerals that is routinely found (albeit in scarce quantities) within iron-nickel meteorites.

Millerite is also called "Capillary Pyrite" since it has a brassy yellow color that is close to the color of pyrite and forms the trademark capillary crystals. When found as brassy sprays inside of sparkling clear quartz geodes, millerite can make a wonderfully attractive and interesting mineral.

 

PHYSICAL CHARACTERISTICS:

  • Color is brassy yellow .
  • Luster is metallic.
  • Transparency Crystals are opaque.
  • Crystal System: Trigonal; bar 3 2/m
  • Crystal Habits include aggregates of acicular (hair-like) or capillary crystals. The aggregates form radial sprays or randomly dispersed individual hairs. Also seen as fibrous coatings and rarely found in granular masses. Millerite is one of several minerals that is found in iron-nickel meteorites.
  • Cleavage is perfect in several directions but is rarely discernible due to the extremely thin crystals.
  • Fracture is uneven.
  • Hardness is 3 - 3.5
  • Specific Gravity is 5.3 - 5.5
  • Streak is dark green to almost black.
  • Other characteristics: may tarnish to a gray color and crystals can be attacked by acids.
  • Associated Minerals calcite, quartz, dolomite, bravoite (basically a nickel-rich pyrite), chalcopyrite, grossular, fluorite and pyrrhotite.
  • Other Characteristics: crystals are not flexible and are brittle.
  • Notable Occurrencesinclude south central Indiana, Keokuk, Iowa, Gap Mine, Pennsylvania and Sterling Mine, New York, USA; Freiberg, Germany; Glamorgan, Wales, England and Sherbrooke and Planet Mines, Quebec.
  • Best Field Indicators crystal habit, associations and environment, color and luster.



 

 

  

THE MINERAL MIMETITE

 

  • Chemistry: Pb5(AsO4)3Cl, Lead Chloroarsenate
  • Class: Phosphates
  • Group: Apatite
  • Uses: As a minor ore of lead and mineral specimens.
  • Specimens

Mimetite shares the same structure with apatite and occasionally crystals of the two will have similar shapes. Mimetite also forms a chemical series with two other minerals; Pyromorphite (Pb5(PO4)3Cl) and Vanadinite (Pb5(VO4)3Cl). This series is a little different than most chemical series which involve substitution of cations such as calcium for magnesium. Instead, this series substitutes its basic chemical units the anion groups; Phosphate (PO4), Arsenate (AsO4) and Vanadate (VO4). Green Mimetite or yellow Pyromorphite can make identification between the two difficult, but usually pyromorphite is green and mimetite is yellow. Vanadinite is usually red. Fortunately for identification purposes, Mimetite does not form well shaped crystals often and especially of the green color. It usually is found as a botryoidal crust, a sparkling cauliflower aggregation or as minute spike-like crystals.

 

PHYSICAL CHARACTERISTICS:

  • Color is typically yellow, orange or brown, less commonly green, colorless or gray.
  • Luster is resinous to adamantine.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is hexagonal; 6/m
  • Crystal Habits include the barrel shaped hexagonal prism with the hexagonal pyramid and/or a pinacoid as a termination. more commonly found as classic botryoidal crusts, sparkling aggregations that resemble cauliflower, small attached spherical masses or as minute spike-like crystals.
  • Cleavage is rarely noticed.
  • Fracture is subconchoidal.
  • Hardness is 3.5 - 4.
  • Specific Gravity is approximately 7.1+ (very heavy for translucent minerals)
  • Streak is off white.
  • Associated Minerals are wulfenite, limonite, calcite, barite, galena and secondary lead deposit minerals.
  • Other Characteristics: Index of refraction is 2.13 (typically high for lead minerals) and crystal terminations can be hollowed out or pitted.
  • Notable Occurrences include Mapimi, Mexico; Arizona, USA and Tsumeb, Africa.
  • Best Field Indicators are crystal habit, high luster, color, and density.

 

The mineral MINASGERAISITE - (Y)


Minasgeraisite is a rare yttrium beryllium silicate. It has a nice color, pale lavender to purple, that is rather attractive. Minasgeraisite is named for the most famous of mineral localities, namely Minas Gerais, Brazil. The name means "mining region" and is the source for not only this rare silicate but for literally hundreds of thousands (if not millions) of fine mineral specimens. It is very fitting that this region has a mineral named for it!

 

PHYSICAL CHARACTERISTICS:

  • Color is lavender to pale purple.
  • Luster is vitreous to dull.
  • Transparency crystals are generally translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include druses and aggregates that form wheat sheaves-like clusters.
  • Cleavage is perfect in one direction.
  • Hardness is 6 - 7
  • Specific Gravity is approximately 4.3 (above average)
  • Streak is purplish white.
  • Notable Occurrence is limited to the type locality from the Jacuaracu Pegmatite at the Jose Pinto Mine, Minas Gerais, Brazil.
  • Best Field Indicators are locality, color, streak, hardness and density.

 

 

    

THE MINERAL MINIUM

 


Minium, which has been known as "red lead", is an oxidation product of other lead minerals. It forms in extreme oxidizing conditions of lead ore bodies and its presence is very indicative of the degree of oxidation. Something of interest to petrologists (rock scientists). It is probably more common than is known as it exists as a slight reddish coating on many lead specimens, often to the detriment of the aesthetic appeal of the underlying mineral. However, some specimens are exceptional and boast a bright red color with a high adamantine luster. The best specimens in the world come from Broken Hill, New South Wales, Australia. Unfortunately, these specimens are the result of a mine fire and mineral purists do not like their human influenced origins.

Minium gets its name from the Minius River in Northwest Spain. The name, minium has also been applied to cinnabar, a red mercury sulfide, but now it is exclusively used world wide to refer to the red lead oxide. Minium is more well known to the makers of pigments than it is to mineral collectors. The artificially produced minium is used as a pigment in paints and dyes although the health concerns of lead have greatly diminished this role.

Minium is a member of the Spinel Group of oxide minerals. The general formula for the Spinel Group is AB2O4. Minium with its formula of Pb3O4, may not look like it belongs. But the lead in minium is actually composed of two different valence states (Pb +2) and (Pb +4). If its formula is rewritten with the different valence states indicated then the formula appears as in classic Spinel Group form as (Pb +4)(Pb +2)2O4. The two different valences of lead occupy different locations in the spinel type structure. Minium's structure is not exactly the same as spinel as spinel is an isometric mineral and minium is a tetragonal mineral. The small size of the lead ions, no doubt, cause a distortion in the spinel structure.

 

THE PHYSICAL CHARACTERISTICS OF MINIUM:

  • Color is red, scarlet to brick-red.
  • Luster is greasy to adamantine.
  • Transparency: Crystals are opaque.
  • Crystal System is tetragonal; bar 4 2 m
  • Crystal Habits include scaly aggregates and powdery coatings on other lead minerals. Also massive and granular. Crystals are generally well striated.
  • Cleavage is perfect in several directions.
  • Fracture is uneven.
  • Hardness is 2.5 - 3.
  • Specific Gravity is 8.9 - 9.2 (Well above average for any mineral).
  • Streak is orange yellow.
  • Other Characteristics: Some specimens fluoresce an orange color under ultraviolet light.
  • Associated Minerals include massicot, galena, wulfenite, pyromorphite, mimetite, bindheimite, cerussite, lead, duftite and sphalerite.
  • Notable Occurrences include its name originator, the Minius River in Northwest Spain as well as Inyo County, California; several localities in Arizona; Leadville, Colorado and at the Jay Gould Mine, Idaho, USA; Broken Hill, New South Wales, Australia; Altai Mountains, Russia; Eifel region of Germany and at Lavrion, Greece.
  • Best Field Indicators are color, crystal habit, streak, density and softness.


     

THE MINERAL MIXITE

 


Mixite is one of just a handfull of bismuth minerals and one of even fewer bismuth arsenates. Other bismuth arsenates include walpurgite and atelestite, to name a couple. Mixite is probably the best known of these, but is still a rare mineral by most considerations. It forms in the oxidation zone of metal ores that probably contained primary bismuth sulfides such as emplectite.

As a mineral collection specimen, mixite is truly a wonderful addition. It forms nice radial clusters called spherules, made up of fine acicular crystals. The color is typically a brilliant green of one shade or another coupled with an attractive silky luster.

Mixite lends its name to a small group of rather obscure minerals called the Mixite Group. The Mixite Group is a group of hexagonal, hydrated copper arsenate and phosphate hydroxides with a general formula of ACu6(XO4)3(OH)6 - 3H2O The A in the formula can be either bismuth, aluminum, calcium, cerium, lanthanum, yttrium, neodymium or thorium. The X can be either arsenic or phosphorous.
These are the members of the Mixite Group:

  • Agardite (Hydrated Lanthanum Yttrium Calcium Cerium Neodymium Copper Arsenate Hydroxide)
  • Goudeyite (Hydrated Aluminum Yttrium Copper Arsenate Hydroxide)
  • Mixite (Hydrated Bismuth Copper Arsenate Hydroxide)
  • Petersite (Hydrated Yttrium Calcium Copper Phosphate Hydroxide)

Agardite actually represents at least a couple of minerals and is sometimes considered a mineral group itself. Agardite and mixite are difficult to differentiate. But if the specimen is associated with other bismuth minerals, than this can prove diagnostic in mixite's favor.

 

PHYSICAL CHARACTERISTICS:

  • Color is green, emerald-green, blue-green, yellow-green or off-white.
  • Luster is vitreous or silky to dull.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is hexagonal.
  • Crystal Habits include radiating clusters, tufts or spherules of acicular or fibrous crystals, also massive, capillary and earthy.
  • Cleavage not noticeable.
  • Fracture is fibrous.
  • Hardness is 3 - 4.
  • Specific Gravity is approximately 3.8 - 4.0 (above average for translucent minerals).
  • Streak is light green.
  • Associated Minerals are pharmacosiderite, zeunerite, emplectite, limonite, malachite, wulfenite, mimetite and barite.
  • Notable Occurrences include Germany; El Carmen Mine, Durango, Mexico; France; Jachymov of the former Czechoslovakia; Inyo County, California and Gila and Pinal Counties in Arizona, USA.
  • Best Field Indicators are color, crystal habit, density and associations with bismuth ores.

 

 

 

 

 

THE MINERAL MOCTEZUMITE

 


Moctezumite is a very rare tellurium mineral discovered in 1965 by Richard Gaines (1917 - 1999), an American minerologist. Its type locality is the Moctezuma Mine, Moctezuma, Sonora, Mexico, hence the name. The Moctezuma Mine is famous for rare telllurium minerals. Other minerals from here include: bambollaite, cliffordite, denningite, emmonsite, spiroffite, tellurium and zemannite. Not only is moctezumite a tellurium mineral, it is also a uranium mineral. The uranium ion in moctezumite is part of a group of ions called the uranyl ion group. The uranyl ion group, UO2, is unusual in that it is a positively charged (+2) ion group. Most ionic groups, especially those that contain oxygen are negatively charged such as the sulfate ion group, SO4-2; carbonate ion group, CO3-2; borate ion group, BO3-3; phosphate ion group, PO4-3; tellurite ion group, TeO3-2 and the silicate ion group, SiO4-4. Another positively charged ion group is the ammonium ion group, NH4+1, found in only a few minerals. Remember, moctezumite is a radioactive mineral and should be stored away from minerals that are affected by radioactivity and of course human exposure should be limited.

 

THE PHYSICAL CHARACTERISTICS:

  • Color is orange to brownish orange.
  • Luster is vitreous to adamantine.
  • Transparency: Crystals are translucent.
  • Crystal System is monoclinic; 2/m.
  • Crystal Habits include small granular crystals.
  • Cleavage is good in one direction.
  • Hardness is 3.
  • Specific Gravity is approximately 5.7 (very heavy for translucent minerals).
  • Streak is pale orange.
  • Other Characteristics: Specimens are radioactive and index of refraction is very high at 2.11 to 2.12.
  • Associated Minerals include various other tellurium minerals such bambollaite, cliffordite, denningite, emmonsite, spiroffite, tellurium, zemannite and other tellurates and tellurites.
  • Notable Occurrences are limited to the type locality of Moctezuma Mine, Moctezuma, Sonora, Mexico.
  • Best Field Indicators are locality, high density, color, radioactivity and cleavage.



 

    

THE MINERAL MOISSANITE

 

  • Chemistry: SiC, Silicon Carbide
  • Class: Native Elements
  • Subclass: Non-metals
  • Group: Carbon
  • Uses: Only as mineral specimens, but artificial material has many uses especially as an abrasive, semi-conductor and as diamond simulants.
  • Specimens

Moissanite is a mineral that was first discovered in fragments of the meteorite at Diablo Canyon or Meteor Crater in Arizona. It was named in honor of its discover Nobel Prize winner, Dr. Ferdinand Henri Moissan. Synthetic moissanite is also known as silicon carbide after its chemistry and by the trade name, carborundum. In the meteoritic material, moissanite is associated with tiny diamonds. Ironically moissanite is the trade name being used for new synthetic SiC gemstones.

Moissanite grown in laboratories is now being cut as gemstones and they are used as diamond simulants. Moissanite brings to the jeweler's table a similar index of refraction and better than twice the fire of diamond, but is only slightly less expensive due to the difficulty in growing the crystals. Moissanite is causing quite a stir in the jewelry markets.

As a diamond simulant, artificial moissanite is very hard to differentiate from diamond and can fool many gemologists. It does have many similarities. It is very hard at 9.25 (diamond is 10) and it is highly refractive with an index of refraction of 2.6 - 2.7 (diamond's IR is slightly lower at 2.42). Most important, moissanite and diamond are thermally conductive unlike other diamond simulants and unfortunately it is this property that is used as the test for the authenticity of real diamonds. Differences however are clear and other tests can be used to differentiate the two. First of all, moissanite is hexagonal, not isometric and therefore it is doubly refractive unlike diamond. A close look at moissanite gemstones should show double facet edges whereas diamond's cut edges are singular in appearance. Moissanite is also slightly less dense than diamond and is rarely perfectly clear of color, having pale shades of green. Also natural flaws are absent in moissanite replaced instead by tiny, unnatural, white, ribbon-like structures that are a result of the growing process. The synthetic SiC known as carborundum has seen many uses in hightech ceramics, electrical components, abrasives, ball bearings, semi-conductors, extremely hard saws and armor.

Natural moissanite is very rare and is limited to iron-nickel meteorites and a few other rare ultra-mafic igneous occurences. Initially there were skeptics to the original meteorite findings and were attributed to the silicon carbide blades that may have been used to saw the type specimens. But this has been disputed because Dr Henri Moissan did not use silicon carbide blades to prepare the samples.

There are several phases of SiC. The original mineral discovered is officially known as moissanite-6H. The (6H) refers to the hexagonal symmetry of this phase of moissanite. There are two other phases recognized as minerals: moissanite-5H and the isometric phase beta-moissanite.

Moissanite is classified as an element dispite the fact, that in chemical reality, it is a compound! The reason for this is that the elemental bonds that exist between carbon and silicon are very similar to the carbon-carbon bonds of other elemental minerals such as diamond. There also is just no other mineral class that moissanite could fit in better than the Native Elements Class! Moissanite in fact is sometimes placed into the Carbon Group which includes diamond and graphite. Additional justification lies in the structure of moissanite which is similar to the structure of diamond. Other chemically unusual Elements Class minerals that are found in meteorites include osbornite {TiN}, cohenite {Fe3C} and schreibersite {(Fe, Ni)3P}.

 

PHYSICAL CHARACTERISTICS:

  • Color is green.
  • Luster is adamantine.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is hexagonal, trigonal and isometric.
  • Crystal Habits include tiny six-sided plates and grains in meteorites.
  • Hardness is 9.25
  • Specific Gravity is 3.1 - 3.2 (average)
  • Streak is white.
  • Other Characteristics: Index of refraction is 2.6 - 2.7, crystals are thermally conductive and highly double refractive.
  • Associated Minerals include iron meteorites and olivine.
  • Notable Occurrences include Diablo Canyon or Meteor Crater in Arizona and as a trace in several kimberlite deposits and placer deposits eroded from them.
  • Best Field Indicator is crystal habit, color, index of refraction, density, thermal conductivity and especially hardness.

 

  

THE MINERAL MOLYBDENITE

 


Molybdenite is a very soft metallic mineral. It can be easily confused with graphite, but not with many other minerals. Graphite has a darker black-silver color and a black-gray to brown-gray streak, whereas molybdenite has a bluish-silver color and streak. Unfortunately, the difference is so slight that it is recommended that the two minerals be seen side by side. Their respective streaks should also be observed side by side to appreciate the differences. If larger samples, free of host rock, are available, then the greater density of molybdenite can be used for identification.

Molybdenite's structure is composed of molybdenum ions sandwiched between layers of sulfur ions. The sulfur's layers are strongly bonded to the molybdenum, but are not strongly bonded to other sulfur layers, hence the softness and perfect cleavage. It is soft enough to leave a mark on paper and fingers. Its greasy feel is due to its extreme softness. Molybdenite or "Moly Ore" as it is sometimes called, is a very high luster mineral and can be an interesting mineral to add to a collection.

 

 

PHYSICAL CHARACTERISTICS:

  • Color is a silver metallic with a bluish cast.
  • Luster is metallic.
  • Transparency crystals are opaque.
  • Crystal System is hexagonal; 6/m2/m2/m
  • Crystal Habits: thin, platy hexagonal crystals terminated by pinacoidal faces, also as tapering six-sided pyramids that can be truncated by the pinacoids. Also massive, lamellar and in small grains in sulfide ore bodies and recrystallized marbles.
  • Cleavage is perfect in one direction, forming thin sheets.
  • Fracture is flaky.
  • Hardness is 1.5 - 2.
  • Specific Gravity is 4.7 to 4.8 (average for metallic minerals)
  • Streak is bluish gray.
  • Associated Minerals include pyrite, wolframite, chalcopyrite, quartz, fluorite, and scheelite.
  • Other Characteristics: thin cleavage sheets and crystals are flexible, but not elastic. It has a greasy feel and leaves marks on fingers.
  • Notable Occurrences Climax, Colorado; Cornwall, England, Raade, Norway; Wilberforce, Ontario and many other Canadian locallities.
  • Best Field Indicators are crystal habit, softness, cleavage, density, bluish streak and color.



 

 

THE MINERAL MONAZITE

 

  • Chemistry: (Ce, La, Th, Nd, Y)PO4, Cerium Lanthanum Thorium Neodymium Yttrium Phosphate.
  • Class: Phosphates
  • Group: Monazite
  • Uses: As an ore of rare earth metals especially thorium, cerium and Lanthanum, radioactive dating uses and as mineral specimens.
  • Specimens
Monazite is actually three different minerals technically, but because of a lack of great differences between them they are referred to as one mineral, monazite. The three monazites have differences in the percentages of their chemical makeup and these differences are reflected in their respective names.


NAME:
FORMULA:
MONAZITE-(Ce)
(Ce, La, Nd, Th, Y)PO4
MONAZITE-(La)
(La, Ce, Nd)PO4
MONAZITE-(Nd)
(Nd, La, Ce)PO4


The differences in the formula represent the greater percentages of certain elements in the mineral. The first element listed in the parenthesis is the element with the greater percentage in the mineral; so that monazite-(La) is greatly enriched in lanthanum, etc. Monazite-(Ce) is not only enriched in cerium it is also by far the most common of the three and is probably the actual mineral when one encounters a specimen that is simply labeled monazite. The general formula represents an aggregate formula for monazite. Silica or SiO4, will often be present in monazite replacing a small percentage of the phosphate groups, but this is not typically shown in monazite's formula. Uranium is also a trace element in some specimens.

The name monazite comes from a Greek word, monazein, which means "to be alone". It is an apt name as it is an allusion to the typical crystal habit of primary origin for monazite as isolated individual crystals in phosphatic pegmatites. Solitary crystals all alone in a dissimilar crystalline matrix. The name does seem to fit.
Monazite is a primary ore of several rare earth metals most notably thorium, cerium and lanthanum. All these metals have various industrial uses and are considered quite valuable. Thorium is a highly radioactive metal and could be used as a replacement for uranium in nuclear power generation. Monazite therefore is an extremely important ore mineral.
Monazite is radioactive, sometimes highly radioactive, and specimens are often metamict. This is a condition found in radioactive minerals and results from the destructive effects of its own radiation on its crystal lattice. The effect can destroy a crystal lattice completely while leaving the outward appearance of the crystal unchanged. Increased metamictation will increase the perfection of the specimens conchoidal fracture. The radioactivity of monazite has been used as an aid in radioactive dating.

Monazite, as already mentioned, forms in phosphatic pegmatites but is actually a standard trace constituent in many ordinary igneous, metamorphic and vein filling rocks. If not too metamict, crystals of monazite are rather durable. They can be weathered out from their host rocks and carried downstream great distances and collect in river deposits and even in ocean beach deposits. Their great density (specific gravity is 4.6 - 5.7) makes it easy for the crystals to be collected into what are called placer deposits.

Placers, as they are informally called, are deposits where heavier objects settle while lighter objects such as sand are constantly removed by the force of water. This process naturally concentrates some pretty valuable stuff. Ores such as rutile and monazite, metals such as gold and platinum and gemstones such as diamonds, rubies, sapphires and spinels, to name a few, are all found in placers. Some monazite beach placers in India alone are so rich that they could supply the entire world's need for monazite for many years to come.

Crystals of monazite are generally simple equant to prismatic crystals that show their monoclinic symmetry without any pretense. Twinning is common and produces crosses and angled reentrant crystals. Specimens of monazite are sought after for their unique chemistry, nice monoclinic form and some specimens are actually quite attractive. Remember, this is a radioactive mineral and should be stored away from other minerals that are subject to damage from radioactivity, and of course human exposure should be limited !

 

PHYSICAL CHARACTERISTICS:

  • Color is yellow to brown or orange-brown.
  • Luster is vitreous, resinous or adamantine.
  • Transparency: Specimens are translucent to opaque, but small crystals can be transparent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include equant to prismatic crystals with wedge-shaped terminations. Crystals are rarely flattened or tabular. Twinning is common forming crosses and variously angled reentrant crystals. Typical habit is granular or massive with no distinct form.
  • Cleavage is perfect in one direction, poor in several other directions. The result is often shards or acutely angled splinters.
  • Fracture is uneven but gradationally converts to conchoidal with metamictation.
  • Hardness is variable from 5 - 5.5
  • Specific Gravity is approximately 4.6 - 5.7 (heavy for translucent minerals)
  • Streak is white.
  • Other Characteristics: Generally highly radioactive which can produce metamictation! A basal parting direction is sometimes noticeable. Crystal surfaces are often etched and pitted.
  • Associated Minerals include apatite, columbite, zircon, xenotime, fergusonite, samarskite, feldspars, quartz, euxenite, polycrase and biotite.
  • Notable Occurrences are wide spread and diverse. They include beach and river sand deposits from Travancore, India; Australia; Brazil; Sri Lanka; Malaysia; Nigeria; Florida and North Carolina, USA. Pegmatite sources include Encampment, Wyoming; Petaca District, New Mexico; Amelia Court House, Virginia; Climax Mines, Colorado; Maine; Alexander and Madison Counties, North Carolina, USA as well as Callipampa, Bolivia; Madagascar; Norway; Austia; Switzerland; Joaquim Felicio, Minas Gerais, Brazil and Finland.
  • Best Field Indicators are crystal habit, color, cleavage shards, high specific gravity, hardness and radioactivity.


THE MINERAL
MONTEBRASITE
  • Chemistry: (Li, Na)AlPO4(OH, F), Lithium Sodium Aluminum Phosphate Hydroxide Fluoride.
  • Class: Phosphates
  • Group: Amblygonite
  • Uses: As a source of lithium and phosphorus and as mineral specimens.
  • Specimens

Montebrasite is an uncommon phosphate mineral, but is perhaps more common than most mineralogist know. It is named for its type locality of Montebras, France. It is found in lithium and phosphate rich pegmatites as a primary mineral. Montebrasite has a fairly compact structure. This fact gives rise to a somewhat high specific gravity. Of course a specific gravity of around 3.05 is not considered very high in the mineral kingdom. But a look at montebrasite's formula shows the elements sodium, lithium, aluminum, hydrogen, fluorine, oxygen and phosphorous. None of these elements are heavy and a mineral composed of these elements would be expected to have a specific gravity much lower than 3.

Montebrasite has lithium in its formula and this gives a reliable lithium result with a flame test. Powdered montebrasite which is placed in a gas flame will produce a brightly colored red flame. This is evidence for the presence of lithium.

There is substitution between the hydroxide and fluorine in montebrasite. It forms a solid solution series with the associated and more common mineral amblygonite and differs from amblygonite by being richer in hydroxide instead of fluorine. The structures of the two minerals are the same and there are no discernible differences in physical properties between the two. Although much rarer than amblygonite, many specimens labeled amblygonite are in fact montebrasite.

 

PHYSICAL CHARACTERISTICS:

  • Color is generally white or creamy, but can also be colorless or pale yellow, green, blue, beige, gray or pink.
  • Luster is vitreous to greasy and pearly on cleavage surfaces.
  • Transparency: Specimens are translucent to less commonly transparent.
  • Crystal System is triclinic, bar 1.
  • Crystal Habits include short prismatic, tabular or equant crystals referred to as lath-shaped, but more commonly found as anhedral masses and compact grains. Twinning forms elongated, flatten crystals.
Lamellar twinning is sometimes seen.
  • Cleavage is in four directions all with varying quality with one direction being perfect, two directions being good and one direction being only distinct. All cleavage angles are non-right angles.
  • Fracture is uneven to conchoidal.
  • Hardness is 5.5 - 6
  • Specific Gravity is approximately 2.98 - 3.10 (slightly above average).
  • Streak is white.
  • Other Characteristics: When powdered and placed in a gas flame, it gives the flame a bright red color and this indicates the presence of lithium. Some specimens are fluorescent orange in long-wave UV light.
  • Associated Minerals include lepidolite, quartz, albite, elbaite, apatite, brazilianite, beryllonite, amblygonite, triphylite, lithiophilite and spodumene
  • Notable Occurrences are Montebras, France; Maricopa and Yavapai Counties, Arizona, USA and other localities where amblygonite is found.
  • Best Field Indicators are density, associations, environment, lithium flame test and especially the numerous cleavage angles.




 

THE MINERAL MONTMORILLONITE

 


Montmorillonite is a member of the general mineral group the clays. It typically forms microscopic or at least very small platy micaceous crystals. The water content is variable, and in fact when water is absorbed by the crystals they tend to swell to several times their original volume. This makes montmorillonite a useful mineral for several purposes. It is the main constituent in a volcanic ash called bentonite, which is used in drilling muds. The bentonite gives the water greater viscosity("thickness" of flow), which is very important in keeping a drill head cool during drilling and facilitating removal of rock and dirt from within a drill hole. Another important use of montmorillonite is as an additive to soils and rocks. The effect of the montmorillonite is to slow the progress of water through the soil or rocks. This is important to farmers with extended dry periods, engineers of earthen dams or levees or perhaps to plug up old drill holes to prevent leakage of toxic fluids from bottom levels to higher aquifers used for drinking water.

As a mineral specimen, montmorillonite does not get much consideration. Usually, pure samples of montmorillonite are massive, dull and not very attractive. However, as with all minerals, there are those exceptional specimens that defy the norm. Montmorillonite has been found as attractive pink inclusions in quartz crystals, and these make for interesting specimens.

 

PHYSICAL CHARACTERISTICS:

  • Color is usually white, gray or pink with tints of yellow or green.
  • Luster is dull.
  • Transparency crystals are translucent and masses are opaque.
  • Crystal System is monoclinic; 2/m.
  • Crystal Habits: never in large individual crystals, usually found in compact or lamellar masses. Also seen as inclusions in quartz as fibers and powder-like masses.
  • Cleavage is perfect in one direction, basal; not seen in massive specimens.
  • Fracture is uneven to lamellar.
  • Hardness is 1- 2 (can sometimes leave marks on paper)
  • Specific Gravity is variable from 2.3 - 3 (average)
  • Streak is white.
  • Other Characteristics: crystals expand to many times their original volume when added to water.
  • Associated Minerals include other clays, garnets, biotite and quartz.
  • Notable Occurances: include sources in France, Italy, USA and many other locallities world wide.
  • Best Field Indicators softness, color, soapy feel, luster and expandability when added to water.



 

 

THE MINERAL MORDENITE

 

  • Chemistry: (Ca, Na2, K2)Al2Si10O24 - 7H2O, Hydrated Calcium Sodium Potassium Aluminum Silicate.
  • Class: Silicates
  • Subclass: Tectosilicates
  • Group: Zeolites
  • Uses: Mineral specimen and chemical filter.
  • Specimens

Mordenite is one of the rarer, but still somewhat more widespread, members of the zeolite group of minerals. Zeolites are a popular group of minerals to collect because they are so beautiful and because they contain such diversity in color, crystal form and rarity (some are very common and easy to collect and some are rare and a pleasure to finally own). Mordenite belongs to this last category.

Zeolites have an openness about their structure that allows large ions and molecules to reside and actually move around inside the overall framework. The structure actually contains open channels that allow water and large ions to travel into and out of the crystal structure. The size of these channels controls the size of the molecules or ions and therefore a zeolite like mordenite can act as a chemical sieve, allowing some ions to pass through while blocking others.
Mordenite forms fine sprays of radial acicular crystal clusters that look like pin-cushions or snowballs. On top of other interesting and beautiful associated minerals, mordenite can be extremely striking. Mordenite is definitely a must have especially for the dedicated zeolite collector.

 

 

PHYSICAL CHARACTERISTICS:

  • Color is colorless, white, yellow, pink and red.
  • Luster is vitreous to silky and pearly.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is orthorhombic; 2/m 2/m 2/m
  • Crystal Habits include sprays of radial acicular crystal clusters that can remind someone of pin-cushions or snowballs. Individual crystals are prismatic to acicular and striated vertically. Aggregates can be radiating, fibrous, columnar and encrusting.
  • Hardness is 4 - 5.
  • Specific Gravity is approximately 2.1 (very light)
  • Streak is white.
  • Associated Minerals are quartz, calcite, chabazite, natrolite, heulandite, stilbite and other zeolites.
  • Notable Occurrences include Morden (hence the name), Kings Co., Nova Scotia, Canada; Hoodoo Mountains, Wyoming and Arizona, USA; Val dei Zuccanti, Italy and Poona, India.
  • Best Field Indicators are crystal habit, color, low density and associations.



 

 

MORGANITE,

The Pink Variety Of Beryl

 

VARIETY INFORMATION:

  • VARIETY OF: Beryl , Be3 Al2 Si6 O18 .
  • USES: Gemstone.
  • COLOR: various shades of pink.
  • INDEX OF REFRACTION: 1.57 - 1.60
  • BIREFRINGENCE: 0.004 - 0.008
  • HARDNESS: 7.5 - 8
  • CLEAVAGE: one direction, poor.
  • CRYSTAL SYSTEM: hexagonal
  • Pleochroic: weak
  • SPECIMENS

Morganite is the pink variety of beryl, the "mother of gemstones". Other gemstone color varieties that belong to beryl include emerald, heliodor, and aquamarine. Other colors of beryl are simply refered to by their color, such as red beryl.
Morganite is colored by trace amounts of manganese that find their way into the crystal structure. It is named after J.P. Morgan, a famous American industrialist. Morganite is found in Brazil, Madagascar, and California, Maine, Connecticut, and North Carolina in the U.S.

 

 

THE MINERAL MOSCHELLANDSBERGITE

 


Moschellandsbergite is an incredibly rare mineral and it has an incredibly long name. It is named for its type locality at Landsberg (formerly known as Moschellandsberg), Obermoschel, Rhineland-Pfalz, Germany. This locality has produced many specimens of various familiar mercury minerals such as cinnabar, mercury and calomel. It also has produced some rather obscure mercury minerals especially mercury alloys such as Belendorffite, Cu7Hg6; Paraschachnerite, Ag3Hg2; Schachnerite, Ag1.1Hg0.9 and of course moschellandsbergite.

Alloys such as moschellandsbergite are classified as elements despite the fact, that in chemical reality, they are compounds! Moschellandsbergite like other alloys have metallic bonds that are very similar to the more pure metallic elements and are thus classified in the Native Elements Class.

 

PHYSICAL CHARACTERISTICS:

  • Color is silver-white to gray.
  • Luster is metallic.
  • Transparency: Specimens are opaque.
  • Crystal System is isometric.
  • Crystal Habits include small rhombic dodecahedral crystal and globular masses.
  • Cleavage is not seen.
  • Fracture is conchoidal.
  • Hardness is 3.5
  • Specific Gravity is 13.6 - 13.7 (well above average, even for a metallic mineral)
  • Streak is gray.
  • Associated Minerals include mercury, calomel, cinnabar and other mercury minerals.
  • Notable Occurrences are limited to the type locality at Landsberg (formerly Moschellandsberg), Obermoschel, Rhineland-Pfalz, Germany.
  • Best Field Indicator is crystal habit, color, locality and density.

 

 

 

 

 

THE MINERAL MOTTRAMITE

 

  • Chemistry: PbCu(VO4)(OH) , Lead Copper Vanadinate Hydroxide
  • Class: Phosphates
  • Group: Descloizite
  • Uses: As a minor ore of lead and copper and as mineral specimens
  • Specimens

Mottramite is an end member of a series composed of the mineral descloizite. Mottramite is the copper rich end member while descloizite is the zinc rich member. Both minerals usually contain significant percentages of both elements and are rarely pure. Mottramite is the rarer of the two minerals. Mottramite can form sparkling crusts that have a nice luster and striking green color. Its rarity and attractiveness are the reason for the typically high prices one would expect to pay for a fine specimen.

 

PHYSICAL CHARACTERISTICS:

  • Color is typically various shades of green, rarely black.
  • Luster is resinous.
  • Transparency: Crystals are transparent to opaque.
  • Crystal System is orthorhombic; 2/m2/m2/m
  • Crystal Habits are typically tiny druzy crusts, radiating and stalactitic masses.
  • Cleavage is none.
  • Fracture is conchoidal to uneven.
  • Hardness is 3 to 3.5.
  • Specific Gravity is approximately 5.7 - 6 (very heavy for translucent minerals)
  • Streak is green.
  • Associated Minerals are descloizite, malachite and other secondary ore minerals.
  • Notable Occurrences include Pinal County, Arizona, USA; Chile; England; Bolivia and elsewhere.
  • Best Field Indicators are color, crystal habit, locallities and density.

 

 

 

 

    

THE MINERAL MURMANITE

 

  • Chemistry: Na2(Ti, Nb)2Si2O9-n(H2O), Hydrated Sodium Titanium Niobium Silicate.
  • Class: Silicates
  • Uses: Only as mineral specimens.
  • Specimens

Murmanite is one of the rarer mineral species found on the Kola Peninsula in Russia. This is one of the classic mineral localities known around the world for producing some truely one-of-a-kind mineral specimens. Murmanite is no exception. Just examining the formula, one can tell that this is a unique mineral. Titanium and niobium are elements not commonly found in the earth's crust. The pink color is attractive and unique, and the luster is beautiful and difficult to describe. This is a good mineral for those interested in rare minerals.

 

PHYSICAL CHARACTERISTICS:

  • Color is pink to purple.
  • Luster vitreous to pearly.
  • Transparency: Crystals are transparent to translucent.
  • Crystal Habits include tabular crystals. Also massive, lamellar and granular.
  • Cleavage is perfect in one direction forming thin sheets.
  • Fracture: is flaky.
  • Hardness is 2 - 3
  • Specific Gravity is approximately 2.75
  • Streak is pale pink.
  • Associated Minerals include minerals such as nepheline, feldspars, epistolite and other rare titanium and niobium minerals.
  • Other Characteristics: Cleavage sheets are elastic.
  • Notable Occurrence is Kola, Peninsula, Russia.
  • Best Field Indicators color, associations, locality and crystal habit.

 

   

THE MINERAL MUSCOVITE

 

  • Chemistry: KAl2(AlSi3O10)(F, OH)2, Potassium aluminum silicate hydroxide fluoride.
  • Class: Silicates
  • Subclass: Phyllosilicates
  • Group: Micas
  • Uses: heat and electrical insulator for industrial purposes.
  • Specimens

Muscovite is a common rock forming mineral and is found in igneous, metamorphic and detrital sedimentary rocks. Muscovite has a layered structure of aluminum silicate sheets weakly bonded together by layers of potassium ions. These potassium ion layers produce the perfect cleavage of muscovite. Although it has such easy cleavage, the cleavage sheets are quite durable and are often found in sands that have undergone much erosion and transport that would have destroyed most other minerals. The sheets of muscovite also have high heat and electrical insulating properties and are used to make many electical components. Muscovite sheets were used for kitchen oven windows before synthetic materials replaced them.

Muscovite is not often valuable as a mineral specimen but is often associated with other minerals of extrodinary beauty and value. Some very nice muscovite crystals accompany such valuable minerals as tourmaline, topaz, beryl, almandine and others. A rare twin variety from Brazil forms yellow five pointed stars and is called "Star Muscovite". A deep green variety is called fuchsite and is colored by chromium inpurities.

 

PHYSICAL CHARACTERISTICS:

  • Color is white, silver, yellow, green and brown.
  • Luster is vitreous to pearly.
  • Transparency crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include tabular crystals with a prominant pinacoid termination. Muscovites four prism faces form diamond shaped "books" and if modified by another pinacoid they form pseudo-hexagonal crystal "books". The sides of the crystal often tend to tapper. Also as lamellar rock forming masses and small flakes in detrital matterial. Twinned crystals can form flat five pointed stars.
  • Cleavage is perfect in one direction producing thin sheets or flakes.
  • Fracture is not readily observed due to cleavage but is uneven.
  • Hardness is 2 - 2.5.
  • Specific Gravity is approximately 2.8 (average)
  • Streak is white.
  • Associated Minerals are quartz, feldspars, beryl and tourmalines.
  • Other Characteristics: cleavage sheets are flexible and elastic, meaning they can be bent and will flex back to original shape.
  • Notable Occurrences include India, Pakistan, Brazil and many USA locallities.
  • Best Field Indicators are crystal habit, cleavage, elastic sheets, color and associations.
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