Saturday, August 20, 2011

Mineral H


THE MINERAL SODALITE

 


Sodalite is a scarce mineral that can be rock forming. Sodalite is named in reference to its sodium content. It is used for carvings and some jewelry pieces. Its light to dark pure blue color is well known in the semi-precious stone trade. Sodalite is a member of the feldspathoid group of minerals. Minerals whose chemistries are close to that of the alkali feldspars but are poor in silica (SiO2) content, are called feldspathoids. As a result or more correctly as a function of the fact, they are found in silica poor rocks containing other silica poor minerals and no quartz. If quartz were present when the melt was crystallizing, it would react with any feldspathoids and form a feldspar.. Localities that have feldspathoids are few but some produce large quantities of sodalite. Sodalite, when not blue, is hard to distinguish from other feldspathoids. It is the only feldspathoid that contains chlorine. Sodalite dissolved in a dilute solution of HNO3 gives a positive chlorine test obtained from some swimming pool test kits.

 

PHYSICAL CHARACTERISTICS:

  • Color is blue, white, gray, or even green.
  • Luster is vitreous or greasy
  • Transparency: Crystals are transparent to translucent, massive specimens are opaque.
  • Crystal System: Isometric; bar 4 3/m
  • Crystal Habits: Dodecahedral crystals have been found, usually massive as a rock forming mineral.
  • Cleavage is poor, in six directions, but rarely seen.
  • Fracture is uneven
  • Hardness is 5.5 - 6.0
  • Specific Gravity is 2.1 - 2.3
  • Streak white
  • Associated Minerals calcite, nepheline, cancrinite and other feldspathoids.
  • Other Characteristics: it is the only feldspathoid to give a positive chlorine test when dissolved in a HNO2 dilute solution.
  • Notable Occurrences include Bancroft, Ontario; Mt. Vesuvius, Italy; Brazil; Ice River area, British Columbia and Maine, USA.
  • Best Field Indicators are color if blue, lack of pyrite association (as in lazurite), hardness and associations.



 

 

THE MINERAL HALITE

 

  • Chemistry: NaCl, Sodium Chloride
  • Class: Halides
  • Uses: Major source of salt and as mineral specimens.
  • Specimens

Halite, better known as rock salt, can easily be distinguished by its taste. Since taste is an important property of salt, there is a right way to taste a specimen of halite (or an unknown mineral that is similar to halite) and a wrong way. The right way is to first lick your index finger, rub it against the specimen and then taste the finger. This limits the amount of the mineral that actually gets in your mouth, an important consideration when you consider that there are poisonous minerals that resemble halite.

Halite is found in many current evaporative deposits such as near Salt Lake City, Utah and Searles Lake California in the U.S., where it crystallizes out of evaporating brine lakes. It is also found in ancient bedrock all over the world where large extinct salt lakes and seas have evaporated millions of years ago, leaving thick deposits of salt behind. The cities of Cleveland and Detroit rest above huge halite deposits that are mined for road salt.

Perfectly formed cubes of halite are typical of the habit of this mineral. However it does form some unusual interesting habits that are much sought after by collectors. One habit is called a hopper crystal which forms what has been termed a skeleton of a crystal. Just the edges of a hopper crystal extend outward from the center of the crystal leaving hollow stairstep faces between these edges. Hopper crystals form due to the disparity of growth rates between the crystal edges and the crystal faces.

Another habit of interest is the vein filling fibrous habit found at Mulhouse, France and at some other locallities. Often specimens are brightly colored purple and blue and with the silky luster due to the fibers, they represent a wonderful and a very uncharacteristic variety of halide. These specimens are a must have for teachers of mineral identification classes that want a stumper for those end of the session ID exams. Of course they are still easy to identify with the oft forgot simple taste test.

Well crystallized specimens of halite cubes can be very impressive and popular. Some are colored an attractive pastel pink by inclusions of bacterial debris that are trapped during crystallization in an evaporative lake. Often these specimens that are sold world wide in rock shops and in mineral shows where grown within the past year. In fact, the crystals form so fast and so well in some evaporative lakes that mineral dealers are using their imaginations to enhance their inventory. They are putting sticks, animal skulls and other imaginative items into these lakes and retrieving them a relatively short time later covered in clusters of white or pink halite cubes.

 

PHYSICAL CHARACTERISTICS:

  • Color is clear or white but can be found blue, purple, pink, yellow and gray.
  • Luster is vitreous.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is isometric; 4/m bar 3 2/m
  • Crystal Habits are predominantly cubes and in massive sedimentary beds, but also granular, fibrous and compact. Some crystals show a crystal type called a hopper crystal discribed above.
  • Cleavage is perfect in three directions forming cubes.
  • Fracture is conchoidal.
  • Hardness is 2
  • Specific Gravity is 2.1+ (light)
  • Streak is white.
  • Associated Minerals include other evaporite deposit minerals such as several sulfates, halides and borates.
  • Other Characteristics: Salty taste.
  • Notable Occurrences include Searles Lake, California and Utah in the U.S., Germany, and Mulhouse, France.
  • Best Field Indicators are taste, cleavage and crystal habit.

 

 

 

 

THE MINERAL HANKSITE

 

  • Chemistry: Na22K(SO4)9(CO3)2Cl, Sodium Potassium Sulfate Carbonate Chloride
  • Class: Sulfates
  • Uses: Only as mineral specimens
  • Specimens

Hanksite is an unusual mineral mostly because of its formula. It is one of only a handful of minerals that contain both carbonate and sulfate ion groups. This brings up the question: to what mineral class does it belong? Some mineral references place it in the carbonates while others put it in with the sulfates. We have placed it in the sulfate class simply because there are more sulfate groups in its structure than carbonate groups.

Hanksite forms very nice crystals in evaporite deposits. These evaporite deposits occur in arid environments. Water, carrying dissolved minerals, floods into a dry lake beds and then just sits. The arid conditions evaporate the water and concentrate the ions. When the water is almost gone, crystals start to form. The mineral halite (salt) is one of the first minerals to crystallize. As the water becomes even more concentrated, eventually rare and unusual minerals such as borax or hanksite will crystallize too. Hanksite crystals can be large and well formed, but are not very complex. Hanksite makes a good addition to any mineral collection.

 

PHYSICAL CHARACTERISTICS:

 

 

 

  

THE MINERAL HARDYSTONITE

 

  • Chemistry: Ca2ZnSi2O7 , Calcium Zinc Silicate.
  • Class: Silicates
  • Subclass: Sorosilicates
  • Group: Melilite
  • Uses: A very minor ore of zinc and as mineral specimens.
  • Specimens

Hardystonite is well known to collectors of fluorescent minerals from Franklin and Sterling Hill, New Jersey. It will fluoresce a dark purple under short-wave ultraviolet light. This fluorescent color is in striking contrast to the normal color of hardystonite. Fluorescence occurs when the ultraviolet light (invisible to humans) imparts energy to some of the atoms in the mineral. This energy is converted by the atom into visible light that we can then see. Hardystonite is usually a dull, unattractive white, but under short-wave UV light it really impresses! The following table shows the more common fluorescing minerals from Franklin and Sterling Hill, New Jersey.

Mineral:
Fluoresces:
Mineral:
Fluoresces:
Mineral:
Fluoresces:
Barite
white
Esperite
yellow
Margarosanite
pale violet
Calcite
red
Fluorite
Violet
Willemite
green
Clinohedrite
orange-yellow
Hardystonite
Violet-blue
Wollastonite
red

These minerals are sometimes found in association with each other and can make for wonderfully colorful fluorescent specimens. The violet-blue color of hardystonite really stands out among these minerals. The combination of hardystonite, clinohedrite and willemite is considered a mineralogical classic. Hardystonite is a product of the metamorphism of zinc minerals, probably hemimorphite and/or smithsonite, that were caught up in the regional metamorphism that created the Franklin site. Hardystonite is found no where else.

 

 

 

 

 

 

PHYSICAL CHARACTERISTICS:

  • Color is white to less commonly pale pink or brown.
  • Luster is vitreous to dull.
  • Transparency: Specimens are translucent to opaque, rarely transparent.
  • Crystal System is tetragonal.
  • Crystal Habits include massive and granular specimens.
  • Cleavage is perfect in two directions and fair in two other directions (all prismatic).
  • Hardness is 3 - 4.
  • Specific Gravity is approximately 3.4+ (above average)
  • Streak is white.
  • Other Characteristics: Fluoresces a dark violet to blue color under short-wave UV light and no fluorescence under long-wave UV light.
  • Associated Minerals include willemite, esperite, zincite, franklinite, calcite and especially clinohedrite.
  • Notable Occurrence is limited to its type locality: North Hill Mine, Franklin, Sussex County, New Jersey, USA.
  • Best Field Indicators are fluorescence, associations, locality and cleavage.

 

 

 

  

THE MINERAL HARMOTOME

 


Harmotome is one of the rarer zeolites, but is popular among zeolite and twin collectors. Its twins are considered classics among collectors who like twinned minerals. If perfectly formed, a twinned crystal of harmotome can appear to be composed of three prismatic crystals grown through the each others center at nearly 90 degree angles. Each termination can look like the end of a blunted phillips head screw driver. The result is a fairly complex looking crystal that is glassy, angular and very attractive.

Harmotome is occasionally found with other zeolites like heulandite and stilbite in the typical zeolite occurrence inside of vesicles or bubbles of volcanic rocks. However it is one of the only zeolites to be found in ore deposits.

Phillipsite is another zeolite that is difficult to distinguish from harmotome. It to commonly forms twins and in fact can form nearly the same twin as harmotome, although less likely to do so. The slightly less dense phillipsite is more likely to be found as aggregates and not as individual twinned crystals and is never found in ore deposits.

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 harmotome can act as a chemical sieve, allowing some ions to pass through while blocking others.

 

PHYSICAL CHARACTERISTICS:

  • Color is colorless, white and yellowish.
  • Luster is vitreous.
  • Transparency: Crystals are transparent to translucent, often milky.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include a classic penetration twinned crystal that is seemingly composed of three prismatic crystals growing through each other at near 90 degree angles. Although examples showing a perfectly formed twin crystal are scarce, twinning is wide spread and almost all crystals of harmotome are twinned. Aggregates can be radiating and columnar.
  • Cleavage is poor in one direction.
  • Fracture is conchoidal to uneven.
  • Hardness is 4.5.
  • Specific Gravity is approximately 2.4 - 2.5 (light, but heavier than most zeolites).
  • Streak is white.
  • Associated Minerals are quartz, heulandite, stilbite, pyrite, brewsterite, edingtonite, barite and other barium and some manganese minerals.
  • Notable Occurrences include several localities in Germany also found at Kongsberg, Norway; Strontian, Highland, Scotland; Wales, Westchester Co., New York, USA and in other localities around the world.
  • Best Field Indicators are crystal habit, twinning, density, hardness and associations.

 

 

 

 

THE MINERAL HAUSMANNITE

 

  • Chemistry: (Mn+2)(Mn+3)2O 4 , Manganese Oxide
  • Class: Oxides
  • Uses: a minor ore of manganese and as a mineral specimen.
  • Specimens

Hausmannite is usually not a beautiful mineral; however some specimens are truly wonderful. It can have a bright metallic luster and form well-shaped crystals. The crystals are tetragonal dipyramids, an eight faced form that looks psuedo-octahedral. Indeed at first look, good crystals of hausmannite appear to be octahedrons like those formed by the spinel group of minerals. The formula of hausmannite, (Mn+2)(Mn+3)2O 4, would also seem to place it in the spinel group. Their general formula is AB2 O4, where A can be a manganese with a positive two charge and B can be a manganese with a positive three (+3) charge. However, those A and B positions are filled with other elements when either one has a manganese ion present. Both sites can not accommodate a manganese ion at the same time and still preserve the isometric structure. Ergo, hausmannite has a distorted spinel structure that produces a tetragonal symmetry and a basal cleavage not possible in the spinel group of minerals. At much higher temperatures, the structure of hausmannite converts to the isometric spinel structure. Hausmannite is an interesting, and can be, when well-formed, a first-rate mineral specimen.

 

PHYSICAL CHARACTERISTICS:

  • Color is dark brown or black.
  • Luster is submetallic to metallic.
  • Transparency: crystals are opaque.
  • Crystal System: tetragonal; 4/m 2/m 2/m
  • Crystal Habits: include the psuedo-octahedral tetragonal dipyramid. Minor pyramidal faces may truncate only the top and bottom points, giving evidence of its tetragonal symmetry instead of the isometric octahedron. Twinning is common and repeated. Also granular and massive.
  • Cleavage is perfect in one direction, basal.
  • Fracture is uneven.
  • Hardness is 5.5
  • Specific Gravity is 4.8+ (average for metallic minerals)
  • Streak is brown.
  • Associated Minerals include psilomelane, pyrolusite, Bixbyite and other manganese minerals.
  • Other Characteristics: dipyramid faces might be horizontally striated (not possible on an octahedron).
  • Notable Occurrences include Batesville, Arkansas, USA; Ilfeld, Germany; Langban, Sweden and the Ural Mountains, Russia.
  • Best Field Indicators are crystal habit, color, hardness, cleavage, density and locality.

 

 

 

  

THE MINERAL HEDENBERGITE

 


Hedenbergite is a rock forming mineral in several metamorphic rocks, especially contact metamorphic rocks and skarns. It is also found in some igneous rocks and ore bodies.

Hedenbergite is a part of an important solid solution series of the pyroxene group. The series includes the minerals diopside, CaMgSi2 O6, and augite, (Ca, Na)(Fe, Mg, Al)(Al, Si)2 O6. Hedenbergite is the iron rich end member of the series. The diopside-hedenbergite series is analogous to the amphiobole, tremolite- actinolite series.

Hedenbergite although usually darker than its gemstone cousin diopside, can still be a wonderful mineral specimen. Its dark green to black color can be stricking with the bright luster that is found on some specimens. While this is not an uncommon mineral, good crystals of hedenbergite are rare and specimens that show nice crystals, good color and luster are prized.

 

PHYSICAL CHARACTERISTICS:

  • Color is black, greenish black, dark green and dark brown.
  • Luster is vitreous to dull.
  • Transparency crystals are translucent to opaque.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include short prismatic (with a square cross section) and accicular, rarely fibrous crystals. Good crystals are rare, more commonly compact, granular, lamellar and massive.
  • Cleavage is perfect in two lengthwise directions at close to right angles and a basal parting direction is sometimes seen.
  • Fracture is uneven to conchoidal.
  • Hardness is 5 - 6
  • Specific Gravity is approximately 3.2 - 3.6 (above average)
  • Streak is white to pale green.
  • Associated Minerals are wollastonite, grossular, andradite, magnetite, actinolite, galena, rhodonite and calcite.
  • Notable Occurrences include Fresno Co., California and Franklin New Jersey, USA; Nordmark Sweden; Broken Hill, Australia and Elba and Tuscany, Italy and Kazakhstan.
  • Best Field Indicators are crystal habit, associations, color, fracture and cleavage.

 

 

THE MINERAL HEDYPHANE

 

  • Chemistry: Pb3Ca2(AsO4)3Cl , Lead Calcium Arsenate Chloride.
  • Class: Phosphates
  • Subclass: Arsenates
  • Group: Apatite
  • Uses: As a very minor ore of lead and as mineral specimens.
  • Specimens
Hedyphane is named from the Greek which is loosely translated as "pleasant appearance". It was first described from the famous Langban Mine in Varmland, Sweden where many unique and exotic minerals have been found. Hedyphane is one of the uncommon members of the Apatite Group of minerals; whose members include the much more common apatites, vanadinite, pyromorphite and mimetite.

 

PHYSICAL CHARACTERISTICS:

  • Color is typically white, gray, bluish or yellowish, but can also be red-violet and green.
  • Luster is greasy to resinous.
  • Transparency: Crystals are translucent to transparent.
  • Crystal System is hexagonal; 6 2 2
  • Crystal Habits include generally massive or granular habits.
  • Cleavage is poor in several directions, but rarely seen.
  • Fracture is uneven.
  • Hardness is 4.5
  • Specific Gravity is approximately 5.8 - 5.9 (rather heavy for translucent minerals)
  • Streak is white.
  • Associated Minerals are richterite, aegirine, hematite, svabite and tilasite.
  • Other Characteristics: Index of refraction is 1.95 (typically high for lead minerals).
  • Notable Occurrences include the type locality at Langban Mine, Filipstad, Varmland, Sweden and other Varmland mines.
  • Best Field Indicators are crystal habit, density, luster, color and locality.




 

HELIODOR,

the yellow variety of beryl


VARIETY INFORMATION:

  • VARIETY OF: Beryl , Be3 Al2 Si6 O18 .
  • USES: Gemstone.
  • COLOR: various shades of yellow.
  • 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

Heliodor is the yellow variety of beryl, the "mother of gemstones". Heliodor does not include golden colors which are given the apt name of golden beryl. Other gemstone color varieties that belong to beryl include emerald, morganite, and aquamarine. Other colors of beryl are simply refered to by their color, such as in golden beryl and red beryl. Heliodor is found in Madagascar, Brazil, North Carolina and California in the U.S., and in Middle Eastern countries and Russia.

 

 

 

 

THE MINERAL HEMATITE

 


Hematite has several varieties, each with their own unique names.
  • Hematite Rose is a circular arrangment of bladed crystals giving the appearance of the flower of a rose.
  • Tiger Iron is a sedimentary deposit of approximately 2.2 billion years old that consists of alternating layers of silver gray hematite and red jasper, chert or even tiger eye quartz.
  • Kidney Ore is the massive botryoidal form and gives the appearance of lumpy kidney-like masses.
  • Oolitic Hematite is a sedimentary formation that has a reddish brown color and an earthy luster and is composed of small rounded grains.
  • Specularite is a micaceous or flaky stone that is sparkling silver gray and sometimes used as an ornamental stone.

Hematite is an important ore of iron and it's blood red color (in the powdered form) lends itself well in use as a pigment. Hematite gets its name from a greek word meaning blood-like because of the color of its powder. Ancient superstition held that large deposits of hematite formed from battles that were fought and the subsequent blood that flowed into the ground. Crystals of Hematite are considered rare and are sought after by collectors as are fine Kidney Ore specimens.

 

PHYSICAL CHARACTERISTICS:

  • Color is steel or silver gray to black in some forms and red to brown in earthy forms. Sometimes tarnished with irredescent colors when in a hydrated form (called Turgite).
  • Luster is metallic or dull in earthy and oolitic forms.
  • Transparency: Crystals are opaque.
  • Crystal System is trigonal; bar 3 2/m
  • Crystal Habits include tabular crystals of varying thickness sometimes twinned, micaceous (specular), botryoidal and massive. also earthy or oolitic.
  • Cleavage is absent however there is a parting on two planes.
  • Fracture is uneven.
  • Hardness is 5 - 6
  • Specific Gravity is 5.3 (slightly above average for metallic minerals)
  • Streak is blood red to brownish red for earthy forms.
  • Associated Minerals include jasper (a variety of quartz) in banded iron formations (BIF or Tiger Iron), dipyramidal quartz, rutile, and pyrite among others.
  • Notable Occurrences especially nice specimens come from England, Mexico, Brazil, Australia and the Lake Superior region.
  • Best Field Indicators are crystal habit, streak and hardness.



 

THE MINERAL HEMIMORPHITE

 



Hemimorphite is one of the more common sorosilicates. Its most noteworthy characteristic is its polar or hemimorphic crystals from where it gets its name. The crystal structure produces a different termination at each end of the crystal. One termination, the "bottom" is rather blunt being dominated by a pedion face while the opposite end, the "top" is terminated by the point of a pyramid. The crystal structure contains tetrahedrons of ZnO3 OH, interlocked with Si2 O7 groups and water molecules. The zinc is at the center of the tetrahedron while the three oxygens, along with an OH group, are at the four points of the tetrahedron. These tetrahedrons are all aligned in the same direction with one face parallel to the pedion termination and the "top" of the tetrahedrons pointing toward the pyramidal termination.

Hemimorphite was originally named calamine but this name had been used for another mineral and hemimorphite was proposed and is now in wide spread use. The hemi means half while the morph means shape and thus hemimorphite is aptly named. Only a few other minerals show hemimorphic character such as tourmaline, but none show it as well as hemimorphite. Clusters of hemimorphite that show well shaped crystals do not always show the hemimorphic character. Because the crystals of a single specimen tend to grow outward with either the "top" or the "bottom" as the overall orientation for that specimen. In order to see the hemimorphic character either a doubly terminated specimen is necessary or two different clusters with different orientations will be needed.

Specimens of hemimorphite tend to be of two very different forms (seems like a trend with this mineral). One form produces very glassy, clear or white, thin, bladed crystals, often well formed showing many crystal faces. Many times these crystals are arranged in fan shaped aggregates. The other form produces a blue to blue-green botryoidal crust that resembles smithsonite or prehnite. Prehnite has a lower density and is usually greener and has different associations with other minerals. Smithsonite has a shimering luster that causes a play of light across the rounded surfaces and has a higher density that hemimorphite. Often hemimorphite will show rough crystal ridges or "cock's comb" structures over top of the basic botryoidal crust. For a collector both forms are a must in their mineral collections.

 

PHYSICAL CHARACTERISTICS:

  • Color is blue-green, green, white, colorless, brown and yellow.
  • Luster is vitreous in large crystals to dull in more compact forms.
  • Transparency crystals are transparent to translucent.
  • Crystal System is orthorhombic; mm2
  • Crystal Habits include the bladed crystal form and the botryoidal form as the most common. The crystals are usually elongated and flat. The terminations are different at each end. One termination is blunted by a pedion face that is usually bevelled by several dome faces. The other end is pointed, being capped by a pyramid. The other common form is botryoidal producing a grape bunch texture. Often the botryoidal form has a cock's comb appearance showing rough crystal terminations.
  • Cleavage is perfect in one direction.
  • Fracture is conchoidal to subconchoidal.
  • Hardness is slightly less than 5.
  • Specific Gravity is approximately 3.4+ (above average)
  • Streak is white.
  • Associated Minerals include limonite, aurichalcite, calcite and smithsonite.
  • Other Characteristics: strongly pyroelectric and piezoelectric.
  • Notable Occurrences include Santa Eulalia and Mapimi, Mexico; New Mexico and New Jersey, USA: England and Zambia.
  • Best Field Indicators are crystal habit, color, density and luster.

 

 

THE MINERAL HERDERITE

 

  • Chemistry: CaBePO4(F, OH), Calcium Beryllium Phosphate Fluoride Hydroxide.
  • Class: Phosphates
  • Uses: As a very minor ore of beryllium and phosphorus and as mineral specimens.
  • Specimens

Herderite is an attractive and except in some mines in New England, a rather scarce phosphate mineral. It forms good crystals and can have a nice yellow or light blue color. Its twinned crystals are its most note-worthy form although its simple prismatic crystals can have quite complex and interesting terminations. The twinning can produce some very non-monoclinic looking crystals that could easily confuse identification. Orthorhombic and nearly hexagonal twins are possible. A "fishtail" twin has also been seen from deposits in Brazil. To top-off this mineral, some specimens are fluorescent. A deep blue color can sometimes be seen under longwave ultraviolet light. Herderite, with its beryllium chemistry, possible fluorescence and both attractive and interesting crystal forms, is certainly a nice addition to anybody's collection.

 

PHYSICAL CHARACTERISTICS:

  • Color is colorless, white, yellowish or pale green to blue-green.
  • Luster is vitreous.
  • Transparency: Specimens are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include prismatic crystals with a complex, but over all domal termination. The prism faces may be rounded and etched. Twinning is common forming cyclic twins that have a malformed hexagonal tabular crystal. The "malformation" usually results in a crystal that looks more orthorhombic than hexagonal and are easily confused with crystals of barite. Other types of twinning can form "fishtail" twins similar to gypsum's famous twins. Also found in nodules, fibrous aggregates, radiating clusters and small grains.
  • Cleavage is indistinct in two directions (prismatic).
  • Fracture is subconchoidal.
  • Hardness is variable from 5 - 5.5
  • Specific Gravity is approximately 2.9 - 3.0 (average)
  • Streak is white.
  • Other Characteristics: Thermoluminescent, meaning it may glow with a weak blue light upon extreme heating (but this test may damage the specimen). Also sometimes fluorescent, showing deep blue in longwave ultraviolet light.
  • Associated Minerals include those minerals common to phosphatic grantite pegamtites.
  • Notable Occurrences include Golconda Mine, Minas Gerais, Brazil; several locations in Germany and Mursinsk, Russia. It the United States there are several locations that produce plentiful supplies of good crystals such as Newry, Stoneham and Topsham, Maine; Fletcher Mine, Alexandria, New Hampshire and San Diego County, California.
  • Best Field Indicators are crystal habit, color, fluorescence if seen, hardness and localities.

 

 

 

 THE MINERAL HESSITE

 

  • Chemistry: Ag2Te, Silver Telluride.
  • Class: Sulfides.
  • Subclass: Tellurides.
  • Uses: As mineral specimens and as a very minor ore of silver and tellurium.
  • Specimens

Hessite is named after the nineteenth century Swiss chemist and Professor of St. Petersburg Mining Institute, Germain Henry Hess. He was the first to analyze specimens of this mineral, some of which were recovered by Gustav Rose in 1829. A synonym of hessite is "silver telluride" which is chemically accurate but is not very mineral like.

Hessite is a telluride mineral, a special group of minerals to collectors. Other tellurides include altaite, a lead telluride; calaverite, a gold telluride; coloradoite, a mercury telluride; empressite, another silver telluride; kostovite, a copper gold telluride; krennerite, a silver gold telluride; melonite, a nickel telluride; petzite, a silver gold telluride; rickardite, a copper telluride and sylvanite, a silver gold telluride. The fondness of tellurium for the precious metals of gold, silver and copper is quite obvious in the preceeding list. Hessite in fact is often found with native gold and native silver. The elemental metal tellurium is also found associated with hessite.

Hessite is generally gray in color and forms pseudo-cubic crystals despite being monoclinic. Its ability to be cut by a knife or its sectility is diagnostic as well as its associations. Hessite is found in hydrothermal veins with the associated minerals mentioned above.

 

PHYSICAL CHARACTERISTICS:

  • Color is a steel gray to lead gray.
  • Luster is metallic.
  • Transparency: Crystals are opaque.
  • Crystal System: Monoclinic; 2.
  • Crystal Habits include pseudo-cubic to prismatic crystals; fibrous and massive forms are also known.
  • Cleavage: Indistinct in one direction.
  • Fracture: Uneven.
  • Hardness is 1.5 - 2
  • Specific Gravity is 8.2 - 8.3 (much heavier than average for metallic minerals)
  • Streak is gray.
  • Other Characteristics: Specimens are sectile.
  • Associated Minerals include gold, quartz, altaite, petzite, sylvanite, chlorargyrite, chlorite, keystoneite, silver, tellurium, coloradoite, thalcusite, tetradymite, sphalerite, chalcopyrite, pyrite, galena and other sulfides.
  • Notable Occurrences include the type locality of Sacaramb (nagyag), Transylvania, Romania as well as San Sebastian and Jalisco, Mexico; Zavodinsk Mine, Altai Mountains, Kazakhstan; Mont Saint-Hilaire, Quebec, Canada and in the United States: Tierra Blanca, Sierra County, New Mexico; Calaveras, Nevada; Cash Mine, Boulder County and Cripple Creek, Colorado; Ross Hannibal Mine, Lawrence County, South Dakota; Tombstone, Arizona; the McAlpine Mine, Tuolumne County and Carson Hill, Calaveras County, California; Eureka Standard Mine, Utah County, Utah and the Flambeau Copper Mine, Ladysmith, Wisconsin.
  • Best Field Indicators are crystal habit, locality, color, sectility, lack of good cleavage, softness and density.

 

 

 

HESSONITE,

the cinnamon-brown to orange variety of grossular garnet

 

VARIETY INFORMATION:

  • VARIETY OF: Grossular garnet, Ca3 Al2 Si3 O12.
  • USES: Gemstone.
  • COLOR: various shades of brown and orange.
  • INDEX OF REFRACTION: 1.73 - 1.75
  • HARDNESS: 6.5 - 7
  • CLEAVAGE: none
  • CRYSTAL SYSTEM: isometric
  • SPECIMENS

Hessonite is one of the gem varieties of the garnet mineral, grossular. The other gem variety of grossular is green and is called Tsavorite. Hessonite is usually cinnamon brown and has been called "cinnamon stone". Hessonite can also be orange; this color is becoming common on the gem markets. Gem quality hessonite is found at Sri Lanka, Brazil and California.

 

 

 

 

 THE MINERAL HEULANDITE

 

  • Chemistry: (Ca, Na)2 - 3Al3(Al, Si)2Si13O36 - 12H2O, Hydrated Calcium Sodium Aluminum Silicate
  • Class: Silicates
  • Subclass: Tectosilicates
  • Group: Zeolites
  • Zeolite Family: Heulandite
  • Uses: As chemical filters and as mineral specimens.
  • Specimens

Heulandite is one of the most common and one of the most well known members of the Zeolite Group. It can have a nice pearly luster and lovely colored hues. It forms wonderfully complex and quite unique crystals and is often associated with other rare and beautiful minerals. Rarely are the larger crystals transparent, but they always have a certain depth of translucency. Heulandite forms large crystals in the petrified bubbles (called vesicles) of volcanic rocks that have had a slight amount of metamorphism. Huelandite occurs in other environments but does not generally form large well shaped crystals in those situations. Heulandite gets its name in honor of John Henry Heuland, a British mineral collector and dealer.

Heulandite's structure is sheet-like. Although still a true tectosilicate where every oxygen is connected to either a silicon or an aluminum ion (at a ratio of [Al + Si]/O = 1/2) and the structure is a framework, there still is a sheet-like structural organization. The sheets are connected to each other by a few bonds that are relatively widely separated from each other. The sheets contain open rings of alternating eight and ten sides. These rings stack together from sheet to sheet to form channels throughout the crystal structure. The size of these channels controls the size of the molecules or ions that can pass through them and therefore a zeolite like heulandite can act as a chemical sieve, allowing some ions to pass through while blocking others. A zeolite can be thought of in terms of a house, where the structure of the house (the doors, windows, walls and roof) is the zeolite while the furniture and people are the water, ammonia and other molecules and ions that can pass in and out of the structure. In the case of heulandite, the sheet-like structure could be analogous to the floors of a high-rise office building with only a few braces between the floors. Heulandite's sheet-like structure produces the prominent pinacoid faces, the perfect cleavage and the unique luster on those faces.
Heulandite shares its structure with the closely related mineral clinoptilolite.Clinoptilolite in fact is considered by some experts to be a high potassium, high silica variety of heulandite. But for now it is considered a distinct species. Natural heulandite specimens can have significant amounts of strontium, potassium, magnesium and barium in their chemical makeup. At times the formula is written to show all these ions and varieties that are enriched in these ions are referred to as strontium rich heulandite for example.

 

PHYSICAL CHARACTERISTICS:

  • Color is colorless, white, gray, green, pink, yellow, red, brown and black.
  • Luster is vitreous to pearly on the most prominent pinacoid face and on cleavage surfaces.
  • Transparency: Crystals are transparent but most commonly translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include blocky crystals described as diamond-shaped, trapezoidal and old fashioned coffin shape with the two faces of a pinacoid usually prominent. Crystals are often modified by secondary faces with pairs of triangular faces very common. Prismatic and acicular forms are also known and are difficult to identify as heulandite. In aggregate specimens this face can be oriented upward producing a crust of curved pearly faces or it can be oriented to the side where the tops of the crystals jut out like the roof tops of a suburban community. Crystals can be simple or complexly modified by a variety of prism and pinacoid faces.
  • Cleavage is perfect in one direction parellel to the prominent pinacoid face.
  • Fracture is uneven.
  • Hardness is 3.5 - 4, maybe softer on cleavage surfaces.
  • Specific Gravity is approximately 2.1 - 2.3 (very light due to the open channels and high water content).
  • Streak is white.
  • Associated Minerals are extensive and include quartz, calcite, apophyllite, barite, pyrite, prehnite, pollucite, tourmaline, scolecite, analcime, chabazite, ferrierite, mordenite, laumontite, natrolite, stilbite and other zeolites.
  • Notable Occurrences are wide spread and include Poona and Nasik Districts, India; Iceland; New Jersey; Washington; Boron, California; Patterson, New Jersey; Arizona and Oregon, USA; Nova Scotia and Quebec, Canada; Iran; Sardinia, Italy; Rio Grande do Sul and Goias, Brazil; New South Wales and Phillip Island, Victoria, Australia; New Zealand; Kola Peninsula, Russia; Scotland and Rhone Valley, Switzerland.
  • Best Field Indicators are crystal habit, density, cleavage, luster and associations.


 

 

THE MINERAL HILAIRITE

 


Hilairite is one of the many new minerals to come from the famous mineral locality, Mont Saint-Hilaire, Quebec, Canada. Hilairite's crystals are small but generally well formed and they have an interesting brown color and a good luster. Its rarity and beauty as well as its ties to this wonderful site make this a great collection mineral if a specimen can be found.

The rocks at Mont Saint-Hilaire are unique because they are the result of an alkaline metal rich intrusion called an agpaitic pegmatite. This pegmatite was also rich in traditionally rarer elements such as titanium, zirconium, cerium, barium and others. Hilairite is certainly one of the minerals that typify this pegmatite having sodium (one of the alkali metals) and zirconium in its chemistry. In fact there are several different minerals that are sodium zirconium silicates that are associated to hilairite. These include the closely related gaidonnayite whose formula, Na2Zr(SiO3)3 - 2H2O only differs in the number of water molecules. Catapleiite is a dimorph of gaidonnayite, having the same chemistry but different structures. The mineral elpidite has a formula of Na2ZrSi6O15 - 3H2O and differs only in the amount and ratio of silica. Of course the structure may be very different.

 

PHYSICAL CHARACTERISTICS:

 

 

 

 

 

THE MINERAL HINSDALITE

 

  • Chemistry: (Pb, Sr)Al3PO4SO4(OH)6, Lead Strontium Aluminum Phosphate Sulfate Hydroxide.
  • Class: Sulfates; although sometimes classified as a Phosphate.
  • Group: Beudantite
  • Uses: Only as mineral specimens.
  • Specimens

Hinsdalite is a rare lead strontium mineral. It forms as a primary or early alteration mineral in sulfide vein deposits with sulfides such as chalcocite, galena, pyrite, sphalerite, covelite and bornite. Hinsdalite is named from the type locality at the Golden Fleece Mine, Lake City, Hinsdale County, Colorado.

Hinsdalite is a difficult mineral to classify in that it has both a phosphate anion group and a sulfate anion group. The phosphate anion group would normally dictate that hinsdalite be classified in the Phosphate Class of minerals. But hinsdalite's sulfate anion is intricate and essential in its structure, while the phosphate anions can be substituted for to at least a limited degree, by other anion groups. Some other classification schemes may place hinsdalite in the Phosphate Class however.

 

PHYSICAL CHARACTERISTICS:

  • Color is yellow, golden-yellow, greenish yellow, green to colorless.
  • Luster is vitreous to greasy.
  • Transparency: Specimens are mostly translucent to small crystals being transparent.
  • Crystal System is trigonal.
  • Crystal Habits include pseudocubic and pseudotetragonal rhombohedrons and modified rhombohedrons. Clusters of spherical flakes and tablets are known. Faces tend to be curved and striated. Granular or massive formations are also seen.
  • Cleavage is perfect in one direction (basal).
  • Fracture: Uneven.
  • Hardness is 4.5.
  • Specific Gravity is approximately 3.7 (above average for non-metallic minerals).
  • Streak is white.
  • Associated Minerals include chalcocite, galena, pyrite, sphalerite, covelite, bornite, pyrophyllite and quartz.
  • Notable Occurrences are limited to the type locality at the Golden Fleece Mine, Lake City, Hinsdale County (hence the name), Colorado as well as locations at Butte, Montana; Ithaca Peak Mine, Mohave County, Arizona and Slate Mountain, El Dorado County, California, USA.
  • Best Field Indicators are crystal habit, color, hardness, density and locality.

 

 

THE MINERAL HODGKINSONITE

 

  • Chemistry: Zn2MnSiO4(OH)2, Zinc Manganese Silicate Hydroxide.
  • Class: Silicates
  • Subclass: Nesosilicates
  • Group: Euclase
  • Uses: A very minor ore of zinc and as mineral specimens.
  • Specimens

Hodgkinsonite is one of several minerals that come from Franklin and Sterling Hill, New Jersey and no where else! It is a product of the metamorphism of zinc minerals, such as hemimorphite and/or smithsonite, that were caught up in the regional metamorphism that created the wonderful Franklin and Sterling Hill sites. Its structure is composed of manganese hydroxide sheets, lnterlayered with sheets of zinc and silicate tetrahedrons. The sheet like structure gives it its perfect basal cleavage.

Hodgkinsonite is named after H. H. Hodgkinson, whom discovered the mineral in 1913. Hodgkinsonite is a very attractive mineral and has even been cut as a gemstone. It has a bright pink to lavender color that is similar to rhodonite, but not quite as red. Hodgkinsonite is most known for its association with snow white barite crystals in veins that cut through the ores composed of willemite and franklinite. It has even been associated with native copper. The attractiveness and color along with the associated minerals have made hodgkinsonite a favorite with collectors of Franklin minerals. Unfortunately the mines have all but completely closed and therefore the only source of hodgkinsonite is material that has already been collected.

 

PHYSICAL CHARACTERISTICS:

  • Color is lavender, violet, pink, brown, yellow, orange to black.
  • Luster is vitreous.
  • Transparency: Specimens are transparent to translucent.
  • Crystal System is monoclinic; 2/m.
  • Crystal Habits include blocky to stubby prismatic crystals. Microcrystals display a acutely sharp pyramidal crystal form. Also massive and vein filling.
  • Cleavage is perfect in one direction (basal).
  • Hardness is 4.5 - 5.
  • Specific Gravity is approximately 3.9 (above average)
  • Streak is white.
  • Other Characteristics: Does not fluoresce often, but some specimens have shown a red fluorescence under longwave UV light.
  • Associated Minerals include barite, willemite, zincite, tephroite, pyrochroite, spessartine, copper, franklinite, calcite and descloizite.
  • Notable Occurrences are limited to its type locality: Franklin and Sterling Hill, New Jersey, USA.
  • Best Field Indicators are locality, color, crystal habit, cleavage and associations.

 

 

 

THE MINERAL HOPEITE

 

  • Chemistry: Zn3(PO4)2 - 4H2O, Hydrated Zinc Phosphate
  • Class: Phosphates
  • Uses: only as a mineral specimen.
  • Specimens

Hopeite is a rare phosphate mineral but is popular among collectors of rare minerals. It forms typically well shaped crystals that are often associated with colorful minerals like lazulite, another phosphate mineral. Hopeite is dimorphous with the mineral parahopeite. The two have the exact same chemistry but different structures. Hopeite is orthorhombic and parahopeite is triclinic.

 

 

 

 

 

PHYSICAL CHARACTERISTICS:

  • Color is colorless, white to off-white, yellow or gray.
  • Luster is vitreous.
  • Transparency crystals are transparent to more commonly translucent.
  • Crystal System is orthorhombic; 2/m 2/m 2/m
  • Crystal Habits include prismatic crystals with a slightly asymmetrical hexagonal outline. Terminations can have simple dome faces or be more complex. Also druzy clusters and compact masses.
  • Cleavage is perfect in one direction.
  • Hardness is 3.0+.
  • Specific Gravity is approximately 3.1 (average for translucent minerals)
  • Streak is white.
  • Associated Minerals are lazulite, parahopeite and some secondary zinc ore deposit minerals.
  • Notable Occurrences include Kabwe, Zambia; Salmo, British Columbia, Canada and Altenburg, Belgium.
  • Best Field Indicators are crystal habit, localities, associations with other zinc ores and/or phosphate minerals and translucency.

 

 

 

THE MINERAL HORNBLENDE

 


Hornblende is actually the name given to a series of minerals that are rather difficult to distinguish by ordinary means. The iron, magnesium and aluminum ions can freely substitute for each other and form what have been distinguished as seperate minerals. The minerals are given the names Magnesio-hornblende, Ferrohornblende, Alumino-ferro-hornblende and Alumino-magnesio-hornblende. These minerals are obviously named for their chemistries although there is little to distinguish them in the field. The iron rich members of the series are more darker black and less likely to be translucent.

Hornblende is not often a collection mineral because good crystals are somewhat difficult to find even though the mineral is widespread. It is almost always opaque and black and not very attractive. However a few specimens are extraordinary and make for valuable specimens. Some crystals can grow to a fairly large size of several feet long and nearly a foot across. Other specimens of hornblende can be acicular clusters or needle thin crystal aggregates. Many times a specimen of a more valuable mineral will be accented by the opaque black crystals of hornblende.

 

PHYSICAL CHARACTERISTICS:

  • Color is almost always black to dark green.
  • Luster is vitreous to dull.
  • Transparency: Crystals are generally opaque but thin crystals or exceptional specimens can be translucent.
  • Crystal System is Monoclinic; 2/m
  • Crystal Habits include short stocky prismatic crystals as well as long thin crystal forms. Crystals can have a hexagonal cross-section although rarely symmetrical. The typical termination, if seen, appears as the two faces of a dome but is actually two of the four faces of a prism. Also found granular, massive and occassionally acicular aggregates.
  • Cleavage is imperfect in two directions at 56 and 124 degrees.
  • Fracture is uneven.
  • Hardness is 5 - 6.
  • Specific Gravity is approximately 2.9 - 3.4 (somewhat above average for translucent minerals)
  • Streak is brown to gray.
  • Other Characteristics: pleochroic in translucent speciments. Large crystals have an almost striated or grainy appearance.
  • Associated Minerals are quartz, feldspars, augite, magnetite, micas and many medium grade metamorphic minerals.
  • Notable Occurrences are numerous and include Bancroft, Ontario; Norway; Bohemia; Mt. Vesuvius, Italy and New York, USA.
  • Best Field Indicators are crystal habit (especially cross-section), color and cleavage.

 

 

 

 

THE MINERAL HOWLITE

 

  • Chemistry: Ca2B5SiO9(OH)5, Calcium Boro-silicate Hydroxide.
  • Classes: Silicates and Carbonates
  • Subclasses: Nesosilicates and Borates
  • Uses: As a source of boron, as an ornamental stone for carved beads, figurines and polished cabochons, as a turquoise substitute and as mineral specimens.
  • Specimens

Howlite, which is named for its discoverer Henry How (a Nova Scotia geologist), is one of those minerals that is more famous for imitating another mineral. In this case the other mineral is turquoise, a phosphate gemstone. Although howlite is always white or gray, it can accept dyes fairly easily and be dyed a turquoise blue. The look of turquoise is so good that dishonest dealers have been unfortunately successful at this hoax. In more honest circumstances, dyed howlite is an affordable substitute for turquoise carvings, beads, polished stones and cabochons. It accepts a nice polish and its porcelaneous luster is attractive and enhances even undyed beads and carvings. Unfortunately it has low hardness, but it still has a distinct toughness. California is the source for almost all of the howlite trade where nodules of up to one hundred pounds have been found.

Howlite is found in continental evaporite deposits with other borate and evaporite minerals. It forms in nodules that appear like the heads of cauliflower, crystals faces on the nodules are rare. Veins of black web-like streaks often are interlaced throughout the nodules, adding to their character. Slabs of howlite are often painted with scenes and designs that make artistic use of these veins. Datolite and bakerite a couple of other boro-silicates, form similar looking nodules, but are distinctively harder. Massive magnesite can also be confused with howlite, but it has good cleavage.

Howlite as is listed above, is often a confusing mineral to classify. The silicon atom in its formula would normally require its classification as a silicate mineral. But some classification schemes prefer to place howlite with other borate minerals in the carbonates class because it has five borons to only one silicon and that its character and formation are more in line with other borate minerals such as colemanite, ulexite, borax and kernite.

 

PHYSICAL CHARACTERISTICS:

  • Color is white with gray to black streaks, web-like markings and blotches.
  • Luster is dull to sub-vitreous (porcelaneous) and earthy.
  • Transparency crystals are opaque to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include cauliflower-like nodules and compact sometimes micaceous masses. Crystals are rare, but minute (1mm size) tabular six sided crystals sometimes aggregated into rosettes are found and some nodules will have crystal faces on their surfaces (mostly from Nova Scotia).
  • Cleavage is absent.
  • Fracture is conchoidal to uneven.
  • Hardness is 3.5
  • Specific Gravity is approximately 2.5 - 2.6 (slightly below average)
  • Streak is white.
  • Other Characteristics: Sometimes fluoresces a blue, yellowish white or off white color under shortwave UV light and dissolves in hydrochloric acid solution without bubbling.
  • Associated Minerals include colemanite, ulexite, anhydrite, gypsum, colemanite and clays.
  • Notable Occurrences include Latonville Quarry, Brookville, Windsor (the type locality) and Iona, Nova Scotia; Newfoundland and New Brunswick, Canada; Sterling Borax Mine, Tick Canyon and Lang, Los Angeles County; Gower Gulch, Inyo County and Daggett, San Bernardino County and other borate deposits in California, USA.
  • Best Field Indicators are nodular character, color, solubility in HCl, luster, lack of cleavage and softness.


 

HUBNERITE

 

  • Chemistry: MnWO4, Manganese tungstate
  • Class: Sulfates
  • Subclass: Tungstates
  • Uses: a minor ore of tungsten (an important industrial element) and as a mineral specimen.
  • Specimens

Hubnerite belongs to a series with another mineral, Ferberite, FeWO4. Hubnerite is the Manganese rich end member while ferberite is the iron rich end member. Wolframite is the name of the series and the name applied to indistinguishable specimens and specimens intermediate between the two end members. Most specimens found in nature fall within 20 - 80% range of the series and these are termed wolframites, (Fe,Mn)WO4. Only if they are more pure than 80% manganese are they called Hubnerite. Hubnerite is more common than ferberite but not nearly as common as wolframite. The iron in wolframite and ferberite cause much of the differences between them and Hubnerite. Hubnerite tends to be light in color, with a lighter streak, more transparent and less dense. Ferberite, however, tends to be black colored, with a black streak, is opaque with a nearly submetallic luster, is denser and weakly magnetic. Wolframite is of course intermediate in characteristics.

Hubnerite can make a valuable and attractive specimen when associated with clear quartz clusters.

 

PHYSICAL CHARACTERISTICS:

  • Color is yellow to reddish brown.
  • Luster is resinous.
  • Transparency crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include the flat, heavily modified, tabular crystals. The crystals are elongated along the c axis and are generally flattened in the a axis direction. Also as columnar aggregates and lamellar masses.
  • Cleavage is perfect in one direction parallel to the a and c axes.
  • Fracture is uneven.
  • Hardness is 4 - 4.5.
  • Specific Gravity is approximately 7.0 (heavy even for metallic minerals)
  • Streak is brown or gray.
  • Associated Minerals are quartz, hematite, tourmalines, cassiterite, micas and pyrite.
  • Other Characteristics: crystals striated lengthwise.
  • Notable Occurrences include Nanling Range, China; France; North Carolina, Idaho and Colorado, USA; Russia; Peru; England and Bolivia.
  • Best Field Indicators are crystal habit, color, density, luster and cleavage.

 

 

THE MINERAL HUMITE

 


Humite is the namesake member of the Humite Group of minerals. Members of the Humite Group are noted for having a mixture of silicate layers and oxide layers in their structures. The silicate layers have the same structure as olivine. The oxide layers have the same structure as brucite. In the case of humite, there are three consecutive olivine layers that alternate between each brucite layer. The most common member of the Humite Group is chondrodite which has only two olivine layers between each brucite layer. Humite is a fairly rare mineral. It is found in hydrothermal veins and contact and regionally metamorphosed dolomitic limestones as small prismatic crystals.

 

PHYSICAL CHARACTERISTICS:

  • Color is commonly yellow, but also white, brown or orange.
  • Luster is vitreous.
  • Transparency: Crystals are translucent.
  • Crystal System: Orthorhombic; 2/m 2/m 2/m
  • Crystal Habits include small prismatic to rounded crystals, but as is most commonly the case, as embedded grains.
  • Cleavage is poor in one direction, basal.
  • Fracture is subconchoidal.
  • Hardness is 6.
  • Specific Gravity is 3.2 - 3.3
  • Streak is white.
  • Associated Minerals include magnetite, diopside, spinel, biotite, serpentine, chondrodite, olivine and calcite.
  • Notable Occurrences are include Monte Somma, Mount Vesuvius, Italy; Paragas, Finland; Varmland, Sweden; Tilly Foster Mine, Brewster, New York, USA and some other localities.
  • Best Field Indicators are color, associations, environment of formation and hardness.

 

 

 

 THE MINERAL HUREAULITE

 

  • Chemistry: Mn5(PO4)2(PO3{OH})2 - 4H2O, Hydrated Manganese Phosphate Hydroxide.
  • Class: Phosphates
  • Uses: Only as mineral specimens.
  • Specimens

Hureaulite is a somewhat rare mineral but is a popular collection mineral. It forms nice clusters of crystals with a pink color. Although the crystals are usually small, they do provide a good sparkle and make for attractive specimens.

Hureaulite's chemistry is unusual in that it has the unusual ion group of PO3{OH}. This group is the same as the regular phosphate ion group except that one of the four oxygens is replaced by an hydroxide or OH group. Sometimes the formula for hureaulite is written as Mn5H2(PO4)4 - 4H2O. The mineral sainfeldite is similar, but with arsenate as the affected ion group.

 

PHYSICAL CHARACTERISTICS:

  • Color is mostly pink, but also found in shades of gray, yellow, red or brown.
  • Luster is vitreous.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include small prismatic crystals with slanted pinacoidal faces sometimes in radiating clusters.
  • Cleavage is absent.
  • Fracture is uneven
  • Hardness is 5
  • Specific Gravity is approximately 3.2 (slightly above average for translucent minerals)
  • Streak is white.
  • Associated Minerals are elbaite, reddingite, rockbridgeite, phosphoferrite and other secondary phosphates.
  • Notable Occurrences include Mesquitela Quarry, Portugal; Rio Grande do Norte-paraiba, Brazil; Palermo Mine, North Groton, New Hampshire and San Diego, California, USA and from where it gets its name, Hureaux, France.
  • Best Field Indicators are color, locality, associations and crystal habit.

 

 

 

THE MINERAL HYDROBORACITE

 

  • Chemistry: CaMgB6O11 - 6H2O, Hydrated Calcium Magnesium Borate.
  • Class: Carbonates
  • Subclass: Borates
  • Uses: As a minor source of boron and as mineral specimens.
  • Specimens

Hydroboracite is an uncommon borate mineral. It is one of the borate minerals that form silky, fibrous crystal clusters. Ulexite is another more common borate that forms similar fibrous aggregates and thus the two minerals are not easy to distinguish. Hydroboracite's silky luster is quite attractive.

 

PHYSICAL CHARACTERISTICS:

  • Color is colorless, white to brownish.
  • Luster is vitreous to silky.
  • Transparency: Specimens are translucent to transparent.
  • Crystal System is monoclinic.
  • Crystal Habits include acicular or fibrous radiating clusters and finely granular masses. Tiny crystals have a wedge-shaped termination.
  • Cleavage is perfect.
  • Fracture is uneven.
  • Hardness is 2 - 3
  • Specific Gravity is approximately 2.2 (below average)
  • Streak is white.
  • Associated Minerals are halite, anhydrite, tunellite, colemanite, ulexite and other borates especially borax.
  • Notable Occurrences include the type locality at Lake Inder, Caucasus Mountains in Southwest Asia; Harz Mountains, Germany; the Furnace Creek Formation of Inyo County and the Boron open-pit mine, Kern County, California, USA.
  • Best Field Indicators are crystal habit, associations, locality, luster and density.

 

 

THE MINERAL HYDROMAGNESITE

 

  • Chemistry: Mg5(CO3)4(OH)2 - 4H2O , Hydrated Magnesium Carbonate Hydroxide.
  • Class: Carbonates
  • Uses: Only as mineral specimens.
  • Specimens

Hydromagnesite is one of those minerals that has a name that sounds more like a chemical than a mineral. It is either named for its chemistry or for being the hydrated relative of magnesite. Other hydrated magnesium carbonates include dypingite, giorgiosite and artinite. Artinite is often associated with hydromagnesite as both are commonly found as alteration products of serpentine, brucite and other magnesium rich minerals. Both minerals can form acicular aggregates although hydromagnesite's crystals are more platy. Hydromagnesite aggregate "puffballs" are sometimes found attached to the needle-like crystals of artinite specimens.

Hydromagnesite is also found in caves as a very unusual cave formation called "bubbles". The bubbles look exactly like chewing gum bubbles and are caused by magnesium rich fluids being forced into the openning of the cave and encountering a viscous film that is pushed outward forming the bubble. The film is a plastic-like, carbonaceous liquid called "moonmilk" that when it eventually dries will crack open and reveal the hydromagnesite precipitate within.

 

PHYSICAL CHARACTERISTICS:

  • Color is colorless to white.
  • Luster is silky, vitreous to earthy.
  • Transparency crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include acicular, lathlike and platy crystals. Tiny spherical aggregates called "puffballs" are found attached to artinite crystals. A type of cave formation called "bubbles" which looks like white chewing gum bubbles are quite unique. Also found as concretions, encrustations and massive.
  • Hardness is 3.5
  • Specific Gravity is 2.15 - 2.25 (very light)
  • Cleavage is perfect in one direction and distinct in another.
  • Fracture is uneven.
  • Streak is white.
  • Other Characteristics: Fluorescent green in shortwave UV and bluish white in longwave UV light and crystals can be striated.
  • Associated Minerals include serpentine, artinite, aragonite, calcite, periclase, brucite, pyrrhotite, talc and olivine.
  • Notable Occurrences include Alameda County; New Idria, San Benito County; Fresno County and other localities in California; Staten Island and Long Island, New York; Jewel Cave, South Dakota and the Grand Canyon, Arizona, USA; Soghan Mine, Kerman, Iran; Eastern Pyrenees, France; Mt. Vesuvius, Italy and British Columbia, Canada.
  • Best Field Indicators are crystal habits, associations, softness and density.

 

 

 

 

THE MINERAL HYDROXYLBASTNASITE

 

  • Chemistry: (Ce, La, Nd)CO3(OH, F) , Cerium Lanthanum Neodymium Carbonate Hydroxide Fluoride.
  • Class: Carbonates
  • Groups: Rare earth carbonates and Bastnasite.
  • Uses: As an important ore of cerium and other rare earth metals and as mineral specimens.
  • Specimens

Hydroxylbastnasite is closely related to its near namesake bastnasite. Hydroxylbastnasite has in its formula and structure hydroxyl ions, OH, that bastnasite lacks, hence the name. The hydroxyl ion groups take the place of most of the fluorines that are found in bastnasite. X-ray studies confirm that the hydroxyl ion groups dramatically increase the unit cells of hydroxylbastnasite structure from that of bastnasite's structure. Crystallographically and mineralogically this is significant. Significant enough to proclaim Hydroxylbastnasite as a unique mineral.

A new proposed mineral has recently been named from specimens that contain all hydroxides and no or very few fluorines. The proposed mineral has a formula of (Ce, La, Nd)CO3OH and is call hydroxylcarbonate-(Nd).This mineral comes from the nickel rich bauxite deposits at Nisi, Greece. The series is then complete with bastnasite (having near 100% fluorines) and hydroxylcarbonate (with near 100% hydroxides) as the two end members and hydroxylbastnasite as the intermediate member.

The structure of the three minerals is made up of stacks of carbonate ion layers and Ce(OH, F) layers. The Ce(OH, F) layers form flat hexagonal sheets with each cerium bonded to three fluorines and visa-versa. The carbonate layers are more complex with angled carbonate triangular groups. The structure is closely studied because it is one of the few rare earth mineral structures that can accommodate variously sized cations.

Hydroxylbastnasite (also spelled hydroxyl-bastnasite) has cerium, lanthanum and neodymium in its generalized formula but officially the mineral is divided into three minerals based on the predominant rare earth element found in specimens. There is Hydroxylbastnasite-(Ce) with a more accurate formula of (Ce, La)CO3(OH, F). There is also Hydroxylbastnasite-(La) with a formula of LaCO3(OH, F). And finally there is Hydroxylbastnasite-(Nd) with a formula of (Nd, Ce, La)CO3(OH, F). There is little difference in the three in terms of physical properties and most hydroxylbastnasite is hydroxylbastnasite-(Ce). Cerium in most natural hydroxylbastnasites usually far and away dominates the others. Hydroxylbastnasite is an ore of cerium, an important industrial metal, but is far behind bastnasite and the phosphate mineral monazite as a source of the rare earth element.
Hydroxylbastnasite is an important ore in the unusual karst, rare earth/nickel-rich/bauxite deposits in Montenegro, Greece and other deposits in the Balkans. These deposits are depleted in fluorine and this the primary reason that hydroxylbastnasite and not bastnasite forms. Hydroxylbastnasite is also found to a lesser extent as a primary mineral in carbonate rich igneous rocks called carbonatites.

 

PHYSICAL CHARACTERISTICS:

  • Color is pale white, yellow or brown.
  • Luster is vitreous, greasy to dull.
  • Transparency: Crystals are translucent to opaque.
  • Crystal System is hexagonal.
  • Crystal Habits include small hexagonal rounded platy crystals forming rosettes and short prismatic crystals. Also found in masses and grains.
  • Hardness is 4.
  • Specific Gravity is 4.7 to 4.8 (well above average)
  • Streak is white.
  • Associated Minerals include hydroxylcarbonate, bastnasite, donnayite, calcite, ewaldite and several bauxite minerals.
  • Notable Occurrences include the Kola Peninsula, Russia; Niksic, Zagrad and Stitovo, Montenegro; Nisi, and Marmeiko nickel rich bauxite deposits, Greece; and several other sites in the Balkans.
  • Best Field Indicators: crystal habit, color, density, luster and locality.

 

 

THE MINERAL HYDROZINCITE

 

  • Chemistry: Zn5(CO3)2(OH)6, Zinc Carbonate Hydroxide
  • Class: Carbonates
  • Uses: minor ore of zinc and as a mineral specimen
  • Specimens

Hydrozincite forms in the oxidation zones of zinc deposits as masses or crusts. Crystals are rare, but can be found. Hydrozincite may be present on many specimens, but is usually unnoticed or assumed to be some other more common mineral, such as calcite or aragonite.

 

PHYSICAL CHARACTERISTICS:

  • Color is white or clear, some tinted pale colors possible.
  • Luster is vitreous or pearly to dull or earthy in massive specimens.
  • Transparency crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include massive forms that can be layered, stalactitic, concretionary, fibrous, and encrusting. Crystal are rare, but when found are usually thin, bladed and tapering to a point or in radiating tufts of acicular crystals.
  • Hardness is 2 - 2.5
  • Specific Gravity is 3.5 - 3.8+ (above average for non-metallic minerals))
  • Cleavage is perfect in one direction.
  • Fracture is uneven or fibrous.
  • Streak is white.
  • Associated Minerals include sphalerite, limonite, smithsonite, hemimorphite and calcite.
  • Other Characteristics: is fluorescent (blue) in UV light and effervesceses easily in cold dilute hydrochloric acid.
  • Notable Occurrences include Iran; England; Austria; Mexico; southwestern USA, and Australia.
  • Best Field Indicators are fluorescense (blue), crystal habits, single plane of cleavage, localities, and reaction to acid.

 

THE MINERAL HYPERSTHENE

 


Hypersthene is a relatively common mineral and is found in igneous and some metamorphic rocks as well as in stony and iron meteorites. It forms a solid solution series with the minerals enstatite and ferrosilite. A solid solution series occurs when two or more elements can substitute for each other in a crystal structure without much alteration of the structure. In this case, the elements are iron and magnesium and enstatite is the magnesium end member of the series. Hypersthene is the intermediate member with around 50% iron and ferrosilite is the iron rich end member of the series. Enstatite is fairly common but ferrosilite is extremely rare. The iron deeply colors the minerals and therefore any deeply colored specimens of this series are usually called hypersthene. In fact the two most common members of the series are often considered together as enstatite-hypersthene in many mineral guides and texts.

Hypersthene is an orthopyroxene or a pyroxene with an orthorhombic symmetry. At high temperatures, hypersthene's structure changes to a structure with a monoclinic symmetry, a clinopyroxene or more specifically, clinohypersthene. Clinohypersthene is a polymorph of hypersthene, meaning that it has the same chemistry but a different structure.
Hypersthene has an ornamental variety. A weathered variety that has a submetallic luster and a bronze like color is called "bronzite". It is sometimes used as an ornamental stone. Both enstatite and hypersthene contribute to the bronzite variety. Some hypersthene is seen on the gemstone markets but is not well known.

The name hypersthene is from the Greek and means "over strength". It is in allusion to its greater hardness than the amphibole mineral hornblende, a mineral with which it is often confused.

 

PHYSICAL CHARACTERISTICS:

  • Color is gray, brown or green.
  • Luster is vitreous to pearly. Weathered specimens can have a submetallic luster ("bronzite").
  • Transparency: Crystals are generally translucent and rarely transparent.
  • Crystal System is orthorhombic; 2/m 2/m 2/m
  • Crystal Habits include rare individual crystals that have a stubby prismatic habit. More typically massive or in coarse lamellar or fibrous aggregates.
  • Cleavage is perfect in two directions at nearly 90 degrees.
  • Fracture is uneven.
  • Hardness is 5 - 6.
  • Specific Gravity is approximately 3.4 - 3.9+ (above average for non-metallic minerals)
  • Streak is white.
  • Other Characteristics: Index of refraction is approximately 1.69 - 1.77.
  • Associated Minerals include iron and stony meteorites, olivine, biotite, quartz, feldspars such as labradorite and certain types of garnets such as almandine.
  • Notable Occurrences include the North Creek, New York, USA and Labrador, Canada.
  • Best Field Indicators are color, crystal habit, hardness, cleavage, index of refraction and luster.


 

THE MINERAL ILMENITE

 

  • Chemical Formula: FeTiO3, Iron Titanium Oxide
  • Class: Oxides and Hydroxides
  • Group: Hematite
  • Subgroup: Ilmenite
  • Uses: As the major ore of titanium, a minor ore of iron, as a flux in blast furnaces, as an abrasive and as mineral specimens.
  • Specimens

Ilmenite is an economically important and interesting mineral. It is named for its place of discovery, such places are called type localities, at Ilmen Lake in the Ilmen Mountains, Miask in the southern portion of the Ural Mountains of Russia. Ilmenite forms as a primary mineral in mafic igneous rocks and is concentrated into layers by a process called"magmatic segregation". It crystallizes out of a magma relatively early before most of the other minerals. As a result, the heavier crystals of ilmenite fall to the bottom of the magma chamber and collect in layers. It is these layers that constitute a rich ore body for titanium miners. Ilmenite also occurs in pegmatites and some metamorphic rocks as well as in the sedimentary rocks that are formed from the weathering and erosion of them.

Since its discovery, the mineral ilmenite has grown greatly in its importance. It is now the most important ore of titanium. Titanium was at one time a metal that had little use and basically no one knew what to do with it. Even as late as 1946 when the metal was finally shown to be capable of being produced commercially, it was considered a "laboratory curiosity". Since that time, titanium has been shown to be a strong aluminum-like metal; light weight, non-corrosive, able to withstand temperature extremes (especially its high melting point, 1800 degrees C) and it has good strength (as strong as steel and twice as strong as aluminum). Titanium alloys have found many applications in high tech airplanes, missiles, space vehicles and even in surgical implants.

Additionally, titanium dioxide TiO2, is a white pigment that is used more and more in paints as lead paint is discontinued due to health considerations. In fact, the largest percentage (up to 95%) of world wide use for titanium is for the production of this white pigment. The pigment has great luster, good endurance, high opacity (it hides whatever is under it, important for paint) and a pure white color. The pigment is also used to provide color for rubber, plastics, textiles, ink, cosmetics, leather, ceramics and paper. Titanium and titanium compounds have found uses in desalination plants, electrical components, glass products, artificial gemstones, jewelry and even as smoke screens. Ilmenite is mined in Australia, Brazil, Russia, Canada, Sri Lanka, Norway, China, South Africa, Thailand, India, Malaysia, Sierra Leone and the United States.

Ilmenite is not the only source of titanium. There are several common to relatively rare titanium minerals such as rutile, sphene, brookite, anatase, pyrophanite, osbornite, ecandrewsite, geikielite and perovskite to name a few. There is at least a small percentage of titanium in many many silicate and oxide minerals as titanium is actually quite a common element (9th most abundant in the Earth's crust). Of all of these minerals, only rutile, with a formula of TiO2, competes with ilmenite for dominance in the titanium source department. Even though rutile is the more common mineral and has a higher percentage of titanium in its formula, it is not concentrated in igneous deposits like ilmenite and is therefore less useful as an ore.

However, in sedimentary detrital deposits known as "placers", both minerals can be concentrated into useable ores. Placers occur when a heavy, resistant mineral is mechanically and gravitationally sorted by natural processes into a recoverable deposit. Placers occur in river bends or behind river obstacles and in ocean shoreline sand deposits where slower water currents allow the heavier minerals to settle. Placer deposits often contain both rutile and ilmenite and there are enough of these deposits around the world to supply us with titanium for decades if not centuries.

Ilmenite is a metallic to submetallic mineral that is generally iron black. At times it can form brightly lustered intricately faceted crystals or radial clusters arranged in a rosette fashion. Platy hexagonal crystals with rhombohedral faces on the edges can appear very similar to hematite's tabular habits. However hematite has a distinctly different streak. Magnetite is also similar and easily confused with ilmenite, but ilmenite has a different crystal form and is not as strongly magnetic. It is often associated with magnetite and therefore ilmenite is a minor ore of iron as the magnetite and ilmenite are processed for their iron contents. Ilmenite by itself is not a profitable iron ore as the titanium inhibits the smelting process.

Ilmenite, hematite and corundum all have similar structures and belong to a more or less informal group called the Hematite Group with a general formula of A 2O3. The structure is composed of alternating layers of cations and oxygens. The cations occupy sites in the layers between the oxygen layers and each are bonded to three oxygens in the above layer and three oxygens in the bottom layer. Not all of the sites available for these cations are occupied as only two out of three are filled. If all the sites were filled, then the formula would be AO in stead of A2O3.

In ilmenite and other members of the Ilmenite Group, alternating layers of cations are occupied by just titanium ions and the other cation layer are occupied only by iron ions and form an ordered sequence of Ti/O/Fe/O/Ti/O/Fe . . . . This effectively lowers the symmetry of ilmenite (which is bar 3) from the other Hematite Group members (which are bar 3 2/m). The other members are more symmetrical because their A cations are all the same and thus there is no ordering of their stacking sequence. Compare the same symmetry phenomena that occurs between the Calcite Group and the Dolomite Group of carbonates.

Ilmenite lends it name to a group of similar, simple, trigonal, titanium oxides called the Ilmenite Group, a subgroup of the Hematite Group of minerals. The general formula for the group is ATiO3; where the A can be either iron, magnesium, zinc and/or manganese. The Ilmenite Group members differ from the other members of the Hematite Group in that the structure is more ordered with the titaniums and A ions occupying alternating layers between the oxygen layers (see above). The oxygen layers are hexagonally packed. Each metal ion is bonded to three oxygens in the oxygen layer above and three oxygens in the layer below. All the members, except for ilmenite, are very uncommon to rare.
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