Saturday, August 20, 2011

Mineral L


THE MINERAL LABRADORITE

 



Labradorite is truely a fascinatingly beautiful mineral. Its a mineral whose charm is not fully noticed and may be overlooked if not viewed from the proper position. Generally a dull, dark looking mineral with no special virtue until the colorful shiller is observed glowing on the surface. Labradorite can produce a colorful play of light across cleavage planes and in sliced sections called labradorescence. The usually intense colors range from the typical blues and violets through greens, yellows and oranges. Some rare specimens display all these colors simultaneously.

The color display is from lamellar intergrowths inside the crystal. These intergrowths result from compatible chemistries at high temperatures becoming incompatible at lower temperatures and thus a separating and layering of these two phases. The resulting color effect is caused by a ray of light entering a layer and being refracted back and forth by deeper layers. This refracted ray is slowed by the extra travel through the layers and mixes with other rays to produce a light ray coming out that has a different wavelength than when it went in. The wavelength could correspond to the wavelength of a particular color, such as blue. The effect depends on the thickness and orientation of the layers. If the layers are too thick or too thin no color shiller is seen. Also if the viewer does not observe from the precise angle or if light is not supplied from the proper angle then no color shiller is seen. The labradorescence is truely a one of a kind mineralogical experience and must be observed in person in order to truely appreciate its beauty.

Labradorite is a member of the plagioclase series of minerals. The plagioclase series comprises felspars that range in chemical composition from pure NaAlSi3 O8 to pure CaAl2 Si2 O8 . Labradorite is defined at approximately the 50% to 70% CaAl2 Si2 O8 . Labradorite by definition must contain 50-70% calcium to 50-30% sodium in the sodium/calcium position of the crystal structure. All members of the plagioclase series usually display lamellar twinning called "Albite Twinning". The twinning is caused by a error in the crystal structure during its growth.

 

PHYSICAL CHARACTERISTICS:

  • Color is gray to smoky black.
  • Luster is dull to vitreous.
  • Transparency crystals are transparent to translucent.
  • Crystal System is triclinic; bar 1
  • Crystal Habits include blocky crystals that rarely form free of the host rock and therefore do not usually show their full crystal forms. In sliced sections of rock, the labradorite appears as blocky chunks with a predominance of near right angled corners. Twinning is common and pervasive so that in labradorite it produces a layered or stacked effect. The twin layers are typically only fractions of millimeters to several millimeters thick. Crystals of labradorite are found imbedded in gabbros and other mafic igneous rocks of low silica content. In anorthosites, labradorite is a main constituent.
  • 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 2.70 - 2.74 (average)
  • Streak is white.
  • Associated Minerals are biotite, pyroxene and hornblende.
  • Other Characteristics: index of refraction is 1.55 - 1.75. Play of colors called labradorescence seen from certain directions can cause flashes of blue, violet and green and sometimes orange and yellow.
  • Notable Occurrences include Labrador, Canada and Scandinavian Pennisula.
  • Best Field Indicators are occurence, twinning striations and labradorescence.

 

 

 

THE MINERAL LARDERELLITE

 

  • Chemistry: NH4B5O6(OH)4, Ammonium Borate Hydroxide.
  • Class: Carbonates
  • Subclass: Borates
  • Uses: Only as mineral specimens.
  • Specimens

Larderellite is a rare borate mineral. It is found at its type locality of Larderello, Val di Cecina, Piza, Toscana, Italy. Larderellite is formed from boron rich waters that steam out of volcanic exhalations. At larderello, the steam is used for the production of boric acid. The larderellite forms crusts that have a cotton ball-like quality and have a snow white color. In addition to the boron in its formula, larderellite has ammounium as well, making it a true chemical oddity in the mineral kingdom. Ammonioborite, (NH4)2B10O16 - 5H2O is another ammonium borate mineral which was also found at larderello.

 

 

PHYSICAL CHARACTERISTICS:

  • Color is white.
  • Luster is vitreous to dull.
  • Transparency: Specimens are translucent.
  • Crystal System is monoclinic.
  • Crystal Habits include puffy, cotton-like crusts.
  • Cleavage is perfect.
  • Fracture is uneven.
  • Hardness is 1
  • Specific Gravity is approximately 1.9 (well below average)
  • Streak is white.
  • Associated Minerals include other rare boron minerals.
  • Notable Occurrence is limited to the type locality of Larderello, Val di Cecina, Piza, Toscana, Italy.
  • Best Field Indicators are habit, locality, luster, softness and density.

 

 

THE MINERAL LAUEITE

 

  • Chemistry: MnFe2(PO4)2(OH)2 - 8H2O, Hydrated Manganese Iron Phosphate Hydroxide.
  • Class: Phosphates
  • Group: Paravauxite.
  • Uses: Only as mineral specimens.
  • Specimens

Laueite is another rare phosphate mineral from the famous Palermo Mine in New Hampshire. The minerals of the Palermo Mine are the results of a phosphate rich pegmatitic intrusion that has undergone extensive alteration. Dozens of unusual, rare and attractive primary and secondary (those formed from the alteration of the primary ones) phosphates have been discovered at this amazing and mineralogically wonderful site. Laueite is just one of these. Although crystals are usually small, they can be well formed. Being composed of manganese, it is little wonder that the mineral is colorful. It has an attractive honey-brown coloration as its typical and most noteworthy color.

Laueite is dimorphous with the mineral stewartite. A dimorph is a mineral that has the exact same formula but different structures. Stewartite is named for the Stewart Mine, Pala, San Diego County, California where the mineral was first described.

 

PHYSICAL CHARACTERISTICS:

  • Color is yellow, orange, honey-brown, orange-yellow or brown.
  • Luster is vitreous.
  • Transparency: Specimens are translucent to transparent.
  • Crystal System is triclinic.
  • Crystal Habits include wedge-shaped to tabular or prismatic crystals and fibrous crusts.
  • Cleavage is perfect.
  • Fracture is conchoidal.
  • Hardness is 3
  • Specific Gravity is approximately 2.4 - 2.5 (average).
  • Streak is white.
  • Associated Minerals include strunzite, stewartite and limonite and others.
  • Notable Occurrences include the Palermo Mine, New Hampshire and the Black Hills region of South Dakota USA; Hagendorf, Germany.
  • Best Field Indicators are color, locality, crystal habit, associations and perfect cleavage.

 

 

  

THE MINERAL LAUMONTITE

 


Laumontite is a handsome mineral. Its columnar crystals can project above the clutter of crystals at its base and appear like a monument above a desert plain. Its crystals can also form smaller, almost acicular jutting prisms that look like a rugged landscape. Although specimens are usually opaque, it retains an alabaster-like luster reminiscent of carved sculpture.

Laumontite's structure has a typical zeolitic 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; therefore, laumontite and other zeolites can act as chemical "sieves".

Zeolites can have a framework, sheet, or chain-like structure. Laumontite's structure is a framework of alumino-silicate tetrahedrons. Laumontite, like other zeolites, commonly forms inside the petrified bubbles (called vesicles) of volcanic rocks that have undergone a small amount of metamorphism. It is often found associated with other zeolites, quartz, gyrolite, calcite, prehnite and apophyllite. These specimens, with such varied associations and forms, can really be fun to collect.

Laumontite is a "must-have" for any zeolite collector, and a real prize for all other mineral collectors as well. Unfortunately, exposure to light causes a loss of water that can destabilize the crystals and cause them to become powdery. It actually dehydrates into a new mineral called leonhardite. It is best to seal crystals in an air tight, lightproof container for storage, and only expose them to light on occassions to admire them. The good news is that this alteration is slow, and a fine specimen can be admired for many years if it is cared for.

 

PHYSICAL CHARACTERISTICS:

  • Color is colorless or white and tinted pink, gray, almond yellow or brown.
  • Luster is vitreous to dull on exposure to light.
  • Transparency: crystals are transparent to translucent and opaque with exposure to light.
  • Crystal System is monoclinic; 2 or m
  • Crystal Habits include nearly square prisms terminated by the flat, slanted face of a pinacoid. also massive, fibrous and radiating. Some good penetration twins are found.
  • Cleavage is perfect in two directions, forming splinters.
  • Fracture is uneven.
  • Hardness is less than 4
  • Specific Gravity is approximately 2.2+ (very light)
  • Streak is white.
  • Other Characteristics: crystals are commonly grooved or striated, and cleavage surfaces have a pearly luster.
  • Associated Minerals are quartz, calcite, apophyllite, babingtonite, heulandite, natrolite and other zeolites.
  • Notable Occurences include Poona, India; Paterson, New Jersey and Pine Creek, California; Iceland and Scotland.
  • Best Field Indicators are crystal habit, luster, density, alteration, and associations.

 

THE MINERAL LAURIONITE

 

  • Chemistry: PbClOH, Lead Chloride Hydroxide.
  • Class: Halides
  • Uses: As a very minor ore of lead and as mineral specimens.
  • Specimens

Laurionite is a rare halide mineral. It is polymorphous with another mineral; paralaurionite. A polymorph is a mineral that shares the same exact chemistry with other minerals but has a different crystal structure. When there are just two minerals involved they are referred to as dimorphs. In the case of laurionite, its structure gives it an orthorhombic symmetry whereas paralaurionite has a monoclinic symmetry.

Both minerals are found in lead slags at only a few localities in the world. Slags are the debris left over from previous mining operations. These slags are generally thought by the miners to be of such low grade ore that they are simply discarded. Often these slag piles are later reclaimed for their now more valuable metals by modern techniques that can extract profitable amounts of metal from these lower grade ores.

Mineralogists often consider these slag piles to be valuable as collecting sites for rare and sometimes unknown minerals. Such is the case for laurionite and paralaurionite. Although both have been known for over a century, like them, many minerals were and are being discovered in lead slag piles, sometimes leftover from mining operations that stopped centuries before.

Laurionite forms small colorless vitreous to adamantine crystals often with distinctive V-shaped striations on the prism faces. Crystals are prismatic to acicular and brittle. Paralaurionite forms minute tabular colorless, white or pale yellow crystals without striations and they are nonbrittle, flexible but inelastic.

 

PHYSICAL CHARACTERISTICS OF LAURIONITE:

  • Color is colorless to white.
  • Luster is vitreous to adamantine.
  • Transparency crystals are transparent to translucent.
  • Crystal System is Orthorhombic.
  • Crystal Habits include striated crystals that are prismatic to acicular with sharply pointed terminations.
  • Cleavage is almost indiscernible in one direction.
  • Fracture is uneven.
  • Hardness is 3 - 3.5
  • Specific Gravity is approximately 6.1 to 6.2+ (very heavy for translucent minerals).
  • Streak is white.
  • Other Characteristics: Crystals are striated with distinctive V-shapes on prism faces and crystals are brittle unlike those of the closely related paralaurionite.
  • Associated Minerals include fiedlerite, cerussite, penfieldite, matlockite, phosgenite and paralaurionite.
  • Notable Occurrences are limited to Laurion, Greece (hence the name) and Wheal Rose, Cornwall, England.
  • Best Field Indicators are crystal habit, associations, striations, brittleness and localities.

 

 

 

 

 

THE MINERAL LAZULITE

 

  • Chemistry: (Mg, Fe)Al2(PO4)2(OH)2, Magnesium Iron Aluminum Phosphate Hydroxide.
  • Class: Phosphates
  • Uses: Mineral specimens, ornamental stone and as a rare gemstone.
  • Specimens

Lazulite is a relatively rare mineral that gets easily confused with other, more well known, minerals. Not only does it sound like the silicate mineral lazurite, it looks like it too! Well, at least it has very similar color to lazulite as well as the carbonate, azurite. The beautiful azure-blue color that is seen in all three of these minerals makes them very desirable as ornamental stones. Azurite is reactive to acids and lazurite forms infrequent and different crystals than lazulite.
Lazulite is in a solid solution series with the mineral scorzalite. A solid solution series is a set of two or more minerals that have a couple of elements that substitute freely for each other. The lazulite-scorzalite series ranges from the magnesium rich lazulite to the iron rich scorzalite. The rarer scorzalite does not differ appreciably, except that it tends to be darker, less transparent and denser than lazulite.

Lazulite is named from an Arabic word for heaven in allusion to its sky blue color. Crystals are more common than massive forms, but localities with gem grade crystals are scattered and scarce. The crystals can be well shaped and show a nice monoclinic dipyramidal to tabular form. Lazulite although most crystals are dull, some exceptional specimens can be quite spectacular.

 

PHYSICAL CHARACTERISTICS:

  • Color is dark azure-blue to a bright indigo blue or even a pale sky blue.
  • Luster is vitreous to dull.
  • Transparency: Specimens are translucent to less commonly transparent.
  • Crystal System: Monoclinic; 2/m
  • Crystal Habits include a dipyramidal form that comes close to looking like a distorted octahedron, usually flattened to the point of being a tabular crystal. Also granular and massive.
  • Cleavage is distinct in one direction.
  • Fracture is uneven.
  • Hardness is 5.5 - 6.
  • Specific Gravity is approximately 3.1 (average for translucent minerals)
  • Streak is pale blue to white.
  • Other characteristics: Clear gemmy crystals show strong pleochroism (yellowish, clear, blue) and crystals are only slightly soluble in warm hydrochloric acid..
  • Associated Minerals are quartz, rutile, kyanite, andalusite, garnets, muscovite, corundum, wardite, brazilianite and siderite.
  • Notable Occurrences: Western Austria; Zermatt, Switzerland; Minas Gerias, Brazil; Lincoln Co., Georgia; Inyo Co., California and Yukon Territory, Canada.
  • Best Field Indicators: color, poor reaction to acids, crystal habit, associations and localities.




 

THE MINERAL LAZURITE

 


Lazurite is a popular but generally expensive mineral. Well-formed, deep blue crystals are rare and valuable. It is more commonly found massive and combined with other minerals into a rock called lapis lazuli.
Lapis lazuli or lapis for short is mostly lazurite but commonly contains pyrite and calcite and some other minerals. The name means "blue rock" and is always a brilliant blue with violet or greenish tints. The rich blue color is due to the sulfur that is inherent in the structure of lazurite. Small crystals of pyrite are always present in lapis and their brassy yellow color is both attractive and diagnostic in distinguishing lapis from its also blue cousin - sodalite rock, which lacks pyrite. The calcite produces white streaks in the lapis and too much calcite will lower the value of the stone.

Lapis lazuli has been mined for centuries from a locality still in use today in the remote mountain valley called Kokcha, Afghanistan. First mined 6000 years ago, the rock was transported to Egypt and present day Iraq and later to Europe where it was used in jewelry and for ornamental stone. Europeans even ground down the rock into an expensive powdered pigment for paints called "ultramarine". Today ultramarine is manufactured artificially. Although now not the only source of lapis, the source in Afghanistan still produces the finest quality material.

Lazurite 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.
The name lazurite is often confused with the bright blue phosphate mineral lazulite. However the two minerals can not be confused with each other identification wise because of lazulite's typical vitreous luster and good crystal habit. The carbonate mineral azurite has a very similar color to lazurite but is associated with the green carbonate mineral malachite and reacts to acids.

 

PHYSICAL CHARACTERISTICS:

  • Color is brilliant blue with violet or greenish tints.
  • Luster is dull to greasy.
  • Transparency: Crystals are translucent to opaque.
  • Crystal System: Isometric; bar 4 3/m
  • Crystal Habits: Dodecahedral crystals have been found, usually massive as a rock (lapis lazuli) forming mineral.
  • Cleavage is poor, in six directions, but rarely seen.
  • Fracture is uneven
  • Hardness is 5 - 5.5
  • Specific Gravity is 2.3 - 2.4 (somewhat below average)
  • Streak is bright blue.
  • Other Characteristics: Index of refraction is 1.5.
  • Associated Minerals calcite, some pyroxenes and most diagnostic pyrite.
  • Notable Occurrences include Kokcha River valley, Afghanistan; Ovalle, Cordillera, Chile; near Lake Baikal, Russia; Mt. Vesuvius, Italy; Cascade Canyon, San Bernardino Mountains and Ontario Peak, California and in the Sawatch Mountains, Colorado, USA.
  • Best Field Indicators are the violet-blue color, pyrite association (unlike sodalite), locality and specific gravity.

NATIVE LEAD

 

  • Chemistry: Pb, Elemental Lead
  • CLASS: Elements
  • GROUP: Gold
  • Uses: Only as mineral specimens. However, processed lead has many uses.
  • Specimens

Lead is extremely rare as a mineral, though the element itself somewhat common. The element lead is found in the Earth's crust in concentration of about 13 parts per billion. Not exactly the most common element, however


 

 

 

 

THE MINERAL LEADHILLITE

  • Chemistry: Pb4SO4(CO3)2(OH)2 , Lead Sulfate Carbonate Hydroxide.
  • Class: Carbonates
  • Uses: Only as mineral specimens.
  • Specimens
Leadhillite is an attractive, brightly lustered and sometimes colorful mineral that is often associated with other rare and beautiful oxidation minerals. Its list of associated minerals reads like a collectors wishlist. Leadhillite is named after its aptly named type locality of Leadhills, Lanarkshire, Strathclyde, Scotland. It forms in the oxidation zone of lead deposits as a secondary mineral, sometimes pseudomorphing other lead minerals and sometimes being pseudomorphed by other lead minerals. A pseudomorph is a mineral that has replaced either the structure or chemistry of an earlier mineral, without distorting the outward shape of the original mineral; thereby producing a crystal that has the shape of one mineral, but is actually either chemically and/or structurally a different mineral. Platy or tabular pseudohexagonal cyclic twinned crystals of leadhillite are the typical habit as well as prismatic crystals. The best specimens have come from Mammoth Mine, Tiger, Arizona. Leadhillite is trimorphous with the minerals macphersonite and susannite. Trimorphs are three different minerals that share the same chemistry, but have different structures. Leadhillite can be quite a popular collection mineral if it were only more available on the mineral markets.

PHYSICAL CHARACTERISTICS:

  • Color is colorless, white, sky blue, pale sea green, yellow and gray. Color usually fades toward the center of the crystals.
  • Luster is resinous to adamantine. Cleavage surfaces are pearly.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m.
  • Crystal Habits include prismatic and tabular or platy crystals; also massive and granular. Pseudohexagonal and pseudorhombohedral twinned crystals are most common and Artini Law twins produce contact twinning. Larger crystals may have a concave basal face. Pseudomorphs after susannite are also seen. Leadhillite is also pseudomorphed by cerussite at times.
  • Cleavage is perfect in one direction (basal) and poor in another.
  • Fracture is conchoidal.
  • Hardness is 2.5 - 3
  • Specific Gravity is 6.3 - 6.6 (very heavy for a translucent mineral)
  • Streak is white.
  • Other Characteristics Some specimens are fluorescent orange.
  • Associated Minerals include malachite, silver, willemite, susannite, wulfenite, dioptase, chalcocite, galena, caledonite, anglesite, linarite and cerussite.
  • Notable Occurrences include the type locality at Leadhills, Lanarkshire, Strathclyde and at other localities in Scotland and at the Campbell Mine, Cochise County; the Grand Reef Mine, Graham County; the Rowley Mine, Maricopa County and the Mammoth-Anthony Mine, Tiger, Pinal County, Arizona; several mines such as the Cerro Gordo Mine in Inyo County and the Blue Bell Mine, San Diego County, California; Coeur D'Alene Mining District, Idaho and Granby, Missouri, USA; Langesundsfjord, Norway and Tsumeb, Namibia.




 

THE MINERAL LEGRANDITE

 


Legrandite is a rare and beautiful mineral that is a favorite of mineral collectors. It is known world wide from the famous localities around Mapimi, Mexico. Legrandite is a vitreous mineral that seems to radiate its unusually rich yellow color. No other mineral is associated with limonite that has a bright yellow color with prismatic crystals and therefore legrandite is pretty easy to identify. However it is rare and not so easy to find. Good specimens are hoarded by the collectors who are lucky enough to find them.

 

PHYSICAL CHARACTERISTICS:

  • Color is straw to orange yellow to colorless.
  • Luster is vitreous.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include prismatic to bladed crystals with a wedge shaped termination often complexly faceted.
  • Cleavage is poor in one direction.
  • Fracture is uneven.
  • Hardness is 4.5 - 5.
  • Specific Gravity is approximately 4.0 (above average for translucent minerals)
  • Streak is white.
  • Associated Minerals are adamite, limonite, pyrite, sphalerite, smithsonite, austinite, paradamite, aragonite, calcite, mimetite and other oxidation zone minerals.
  • Notable Occurrences include the famous mines at Mapimi, Mexico as well as Flor de Pena Mine, Mexico.
  • Best Field Indicators are color, luster, density, associations and crystal habits.

 

 

 

 

 

THE MINERAL LEIFITE

 

  • Chemistry: Na6Be2Al2Si16O39(OH)2 - 1.5H2O; Hydrated Sodium Beryllium Aluminum Silicate Hydroxide Fluoride.
  • Class: Silicates
  • Subclass: Tectosilicates
  • Uses: Only as a mineral specimen.
  • Specimens

Leifite is a rather rare and obscure beryllium silicate mineral. It forms in rare rocks known as agpaites which are igneous rocks of unusual concentrations. They are characterized by high concentrations of alkali metals especially sodium and low concentrations of silicon and aluminum. They are feldspar and feldspathoid rich and being low in silicon, contain little or no quartz. Agpaite pegmatites contain unusual minerals because they originate with unusual elements. Elements such as beryllium, zirconium, titanium, niobium, barium, strontium, thorium and rare earth metals are all found in the compositional mix that represents this rock type.

There exists agpaite in several places around the world, but by far the most famous are the ones at the Kola Peninsula in Russia, Narsarsuk, Greenland and the one above all the rest, the mines of Mount Saint Hilaire, Quebec. Leifite is one of the rare minerals that can form in these silica starved, unique chemical environments. Other minerals coming from these unique localities include catapleiite, synchysite, serandite, elpidite, aegirine arfvedsonite, eudialyte and analcime to name a few.

 

PHYSICAL CHARACTERISTICS:

  • Color is white or colorless.
  • Luster is vitreous.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is trigonal.
  • Crystal Habits include prismatic to acicular crystals with a hexagonal cross-section and a basal termination. Crystals are striated lengthwise. Aggregates are clustered into radial sprays.
  • Hardness is 6.
  • Specific Gravity is 2.6
  • Streak is white.
  • Associated Minerals are calcite, aegirine and other rare minerals.
  • Notable Occurrences include Narsarsuk, Greenland and Mount Saint Hilaire, Quebec.
  • Best Field Indicators are crystal habit, locality and hardness.

THE MINERAL LEPIDOLITE

 

  • Chemistry: KLi2Al(Al, Si)3O10(F, OH)2, Potassium lithium aluminum silicate hydroxide fluoride.
  • Class: Silicates
  • Subclass: Phyllosilicates
  • Group: Micas
  • Uses: ore of lithium, ornamental stone and heat insulator for industrial purposes.
  • Specimens

Lepidolite is an uncommon mica and has only in the past decade become available on the mineral market in large quantities. Lepidolite is an ore of lithium and forms in granitic masses that contain a substantial amount of lithium. The lithium content in lepidolite does vary greatly however and low lithium lepidolite is nearly useless as an ore of lithium. The typical violet to pink color of lepidolite is characteristic and is the only field test available to identify lepidolite from other micas. Pink muscovite or very pale lepidolite may confuse an identification.

Lepidolite, like other micas, has a layered structure of lithium aluminum silicate sheets weakly bonded together by layers of potassium ions. These potassium ion layers produce the perfect cleavage. lepidolite crystals accompany such other lithium bearing minerals such as tourmaline, amblygonite and spodumene and can add greatly to the value of these specimens. A rock made of granular pink lepidolite and red to pink tourmaline is used as an ornamental stone for carving. Single large plates or "books" of lepidolite can have appealling violet color and make attractive mineral specimens.

 

PHYSICAL CHARACTERISTICS:

  • Color is violet to pale pink or white and rarely gray or yellow.
  • Luster is vitreous to pearly.
  • Transparency crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include tabular to prismatic crystals with a prominant pinacoid termination. Lepidolite's four prism faces and two pinacoid faces form pseudo-hexagonal crystal "books". The sides of the crystal often tend to tapper. Also as micaseous, lamellar or granular rock forming masses.
  • Cleavage is perfect in one direction producing thin sheets or flakes.
  • Fracture is not readily observed due to cleavage but is uneven.
  • Hardness is 2.5.
  • Specific Gravity is approximately 2.8+ (average)
  • Streak is white.
  • Associated Minerals are quartz, feldspars, spodumene, ambygonite and tourmaline especially elbaite.
  • Other Characteristics: cleavage sheets are flexible and elastic, meaning they can be bent and will flex back to original shape. Also some specimens may show triboluminescence.
  • Notable Occurrences include Brazil; Ural Mountains, Russia; several African localities and California, USA.
  • Best Field Indicators are crystal habit, color, cleavage, elastic sheets and associations.


     

THE MINERAL LEUCITE

 

Leucite is a popular and interesting mineral. Its name comes from the greek word for "white" in allusion to its typical color. At high temperatures, leucite is isometric and will form the isometric trapezohedron crystal form. Interestingly, as leucite cools, the isometric structure becomes unstable and transforms into a tetragonal structure without altering the outward shape. Although the mineral is actually tetragonal, the outward shape is pseudo-isometric and thus the crystal form is actually pseudo-trapezohedral.

Leucite is one of the few minerals that forms the unique trapezohedron. The trapezohedron has 24 deltoid shaped faces, where each face occupies one third of the position of a single octahedron's face. The minerals of the garnet group and the mineral analcime are the only common minerals that will also form the trapezohedron.

Distinguishing leucite from the garnets and analcime is relatively easy in some cases. The garnets are much harder and usually deeply colored. Leucite has a much lower density and usually has a duller luster than analcime. Also leucite is typically embedded in host rock where as analcime, when displaying good crystals and not massive or granular, is loose or attacted to other minerals in volcanic cavities.

Leucite, KAlSi2O6 is actually distantly related to analcime, NaAlSi2O6-H2O. Leucite is a member of the feldspathoid group of minerals. Analcime, although usually considered a zeolite, is sometimes placed in the feldspathoid group since its chemistry and occassional occurrences are similar.

Minerals whose chemistries are close to that of the alkali feldspars but are poor in silica (SiO2) content, are called feldspathoids. Leucite, like other feldspathoids, is 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..

At one time leucite was used as a source of potassium and aluminum. Probably due to the high aluminum to silicon ratio, its structure is easily destroyed by acids and this frees the aluminum ions.
Leucite, already a pseudomorph from a high temperature phase, commonly is altered to pseudoleucite. Pseudoleucite is not a mineral but a mixture of nepheline, orthoclase and analcime.

 

PHYSICAL CHARACTERISTICS:

  • Color is clear, white or gray, with yellowish and reddish tints possible.
  • Luster is vitreous or greasy to dull.
  • Transparency: crystals are transparent, translucent to commonly opaque.
  • Crystal System is isometric; 4/m bar 3 2/m at temperatures above 605 degrees C, and tetragonal; either 4 2 2 or 4/m, below 605 degrees C.
  • Crystal Habits include the characteristic trapezohedron (actually pseudo-trapezohedron). Also granular and massive.
  • Cleavage is absent.
  • Fracture is conchoidal
  • Hardness is 5.5 - 6.
  • Specific Gravity is approximately 2.4 - 2.5 (slightly below average)
  • Streak is white.
  • Associated Minerals include olivine, labradorite, augite, biotite, nepheline and other feldspathoids.
  • Other Characteristics: surface is usually pitted, dull or has a weathered look.
  • Notable Occurrences include Mt. Vesuvius, Italy; Magnet Cove, Arkansas, Leucite Hills, Wyoming and Litchfield, Maine, USA; Brazil and Hastings Co, Ontario.
  • Best Field Indicators are crystal habit, density, low hardness, luster and associations.




 

 

THE MINERAL LEUCOPHANITE

  • Chemistry: (Na, Ca, Ce)2BeSi2(O, OH, F)7, Sodium Calcium Cerium Beryllium Silicate Hydroxide Fluoride.
  • Class: Silicates
  • Subclass: Sorosilicates
  • Group: Melilite - Fresnoite
  • Uses: Very minor source of cerium and as mineral specimens.
  • Specimens
Leucophanite is a rare beryllium silicate that was first discovered from the mines of Langesundsfjord district of Norway, a classic mineral locality filled with rare minerals. It was discovered early in the areas mining history and was one of the first minerals described from there in 1840. Of interest was the trace amounts of rare earth elements in its chemistry, especially cerium which substitutes for some calcium. Leucophanite is also found at Mont Saint-Hilaire, Quebec, Canada from where some of the best specimens are found. Another classic locality from where this mineral comes from is the Lovozero intrusion on the Kola Peninsula, Russia. All these locations have unusual rocks that are quite unique and are called agpaitic pegmatites.

Leucophanite forms nice crystals that belie their true symmetry. They appear to be tetragonal or even cubic forming rectangular box or cube shaped crystals. But their true symmetry is triclinic, pedion class which is the lowest symmetry possible in a three dimensional system. The only symmetry element is translational shift as it lacks any mirrors, rotations, or even a center. The symmetry is noted by a 1 which represents a one fold rotation (as in if you rotate the crystal one full 360 degree turn, it will look the same as when you started; overstating the obvious). Crystals from minerals that belong to this class can be fascinating with their complex non-symmetrical faces. Unfortunately leucophanite does not show its true symmetry but exhibits an impostor symmetry, and a rather ordinary one at that.

Leucophanite is named for the white flashes that are seen as a crystal is rotated. Leucophanite loosely translated from the Greek means "white appearing". There are a few similar sounding minerals such as leucophoenicite, leucophosphite, leucosphenite and even leucite. But leucophanite is very different from all of these. A synonm of leucophanite is "leucophane" which is not official but is still in limited use.

 

PHYSICAL CHARACTERISTICS:

  • Color is white to yellowish, yellow and green.
  • Luster is vitreous.
  • Transparency: Specimens are translucent to transparent.
  • Crystal System is triclinic, 1.
  • Crystal Habits are pseudotetragonal and pseudocubic forming rectangular box or cube shaped crystals. Penetration twinning is common and forms flat square and elongated crystals. Aggregate rosettes are also seen.
  • Cleavage is perfect in one direction and fair in two others.
  • Hardness is 4.
  • Specific Gravity is approximately 3.0 (average)
  • Streak is white.
  • Associated Minerals include many rare and beautiful minerals such as aegirine, fluorite, rhodochrosite, serandite, albite, astrophyllite, natrolite, rhabdophane, analcime, ancylite, catapleiite, epididymite, microcline and behoite.
  • Notable Occurrence includes the type locality of Langesundsfjord district, Norway as well as Mont Saint-Hilaire, Quebec, Canada and Kola Peninsula, Russia.
  • Best Field Indicators are crystal habit, color, associations, locality and cleavage.



 

 

THE MINERAL LIBETHENITE

 

  • Chemistry: Cu2PO4(OH), Copper Phosphate Hydroxide
  • Class: Phosphates
  • Uses: mineral specimens
  • Specimens

Libethenite is a rare secondary copper mineral that is noted for its deep green color. It is found in deeply weathered, highly concentrated copper sulfide ore bodies. Libethenite is isostructural with the minerals olivenite, Cu2AsO4(OH) and adamite, Zn2AsO4(OH). This means that they share the same symmetry and crystal shapes. Libethenite's emerald green color and bright luster give it a well earned place in anyones collection.

 

 

 

 

 

 

 

PHYSICAL CHARACTERISTICS:

  • Color is dark emerald to olive green.
  • Luster is resinous to vitreous.
  • Transparency: Specimens are translucent.
  • Crystal System: is orthorhombic 2/m2/m2/m
  • Crystal Habits include crystals that are diamond-shaped, often acicular, prisms that are terminated by a dome with triangular faces, also as tiny crystalline druzes, fiberous masses, nodules and crusts.
  • Cleavage is good in two directions.
  • Fracture is subconchoidal to uneven.
  • Hardness is 4
  • Specific Gravity is approximately 3.6 - 3.9 (above average for translucent minerals)
  • Streak is olive green.
  • Other Characteristics: Slightly soluable in hydrochloric acid.
  • Associated Minerals are malachite, olivenite, quartz, limonite, adamite, brochantite and other secondary copper ore minerals.
  • Notable Occurrences: Cornwall, England; Libethen (hence the name), Romania; Zaire; Russia and California, Utah and Arizona, USA.
  • Best Field Indicators are color, streak, crystal habits, associations and density.

 

 

 

 

    

THE MINERAL LIMONITE

 

  • Chemistry: A mixture of hydrated iron oxides
  • Class: Oxides and Hydroxides
  • Uses: Important ore of iron, as a pigment and as mineral specimens.
  • Specimens

Limonite is not a true mineral but a mixture of similar hydrated iron oxide minerals. Most of limonite is made up of Goethite. Massive Goethite and Limonite can be indistinguishable. Limonite forms mostly in or near oxidized iron and other metal ore deposits, and as sedimentary beds. Limonite has been known to pseudomorph other minerals such as pyrite, meaning it replaces a crystal of pyrite with limonite but keeps the shape of the pyrite crystal.

 

PHYSICAL CHARACTERISTICS:

  • Color is yellow, orange, reddish brown, brownish black.
  • Luster is earthy to dull.
  • Transparency is opaque.
  • Crystal System is undefined.
  • Crystal Habits include massive, layered, botryoidal and stalactitic.
  • Cleavage is absent.
  • Fracture is crumbly or earthy.
  • Hardness is variable 4 - 5.5
  • Specific Gravity is variable at 2.9 to 4.3 (average to above average)
  • Streak is brownish yellow to yellow.
  • Associated Minerals include a large list of minerals particularly secondary deposit minerals.
  • Notable Occurrences include many iron mines around the world, especially nice specimens come from Europe, Mexico, Canada and northeastern USA.
  • Best Field Indicators are lack of crystal forms, lack of cleavage and streak.





 

THE MINERAL LINARITE

 

  • Chemistry: PbCuSO4(OH)2, Lead Copper Sulfate Hydroxide.
  • Class: Sulfates
  • Uses: mineral specimens
  • Specimens

Linarite is colored a bright azure blue color. This beautiful and somewhat rare mineral is usually found as crusts of small crystals. Even with the small crystals, the color is always intense. Azurite is a mineral that can be easily confused with linarite. However, linarite does not react at all to dilute hydrochloric acid. Linarite is formed from the oxidation of lead and copper minerals such as galena and chalcopyrite. The color is impressive for the tiny sparkling crystals. One look at the mineral will convince most collectors that they need an example of linarite in their collections.

 

PHYSICAL CHARACTERISTICS:

  • Color is bright azure blue.
  • Luster is vitreous to adamantine to earthy in massive specimens.
  • Transparency crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include prismatic crystals and more rarely platy to tabular, all crystals tend to have multiple facets. Crystals are always tiny to small growing off encrustations on host rocks. Also as earthy masses.
  • Cleavage is perfect in one direction but only seen in the larger crystals.
  • Fracture is conchoidal.
  • Hardness is 2.5.
  • Specific Gravity is approximately 5.3+ (very heavy for translucent minerals, but hard to obtain from encrusting specimens)
  • Streak is blue.
  • Associated Minerals are galena, chalcopyrite, brochantite, malachite and cerussite.
  • Other Characteristics: some specimens show an alignment of crystals.
  • Notable Occurrences include Tiger, Arizona and Butte, Montana, USA; Leadhills, Scotland; Spain and Argentina.
  • Best Field Indicators are crystal habit, associations, color and lack of reaction to acid.



 

THE MINERAL LINNAEITE

 

  • Chemistry: Co3S4, Cobalt Sulfide.
  • Class: Sulfides
  • Uses: As an important ore of cobalt and as mineral specimens.
  • Specimens

Linnaeite is not a well known mineral but is still an important ore of the strategically valuable metal cobalt. It commonly forms with other cobalt sulfides but usually as just a trace. In a few areas it has formed in large quantities and has become a valuable ore in mines in Zaire and Zambia.

 

PHYSICAL CHARACTERISTICS OF LINNAEITE:

  • Color is gray to white, usually with a tarnish if exposed to weathering.
  • Luster is metallic.
  • Transparency crystals are opaque.
  • Crystal System is isometric.
  • Crystal Habits include small octahedral crystals, usually well formed, and as granular masses in sulfide rocks.
  • Cleavage is imperfect.
  • Fracture is uneven.
  • Hardness is 4.5 - 5.5
  • Specific Gravity is approximately 4.8 (average for metallic minerals)
  • Steak is black.
  • Other Characteristics: A red to violet tarnish forms on weathered specimens.
  • Associated Minerals include covellite, chalcocite bornite and chalcopyrite
  • Notable Occurrences include Katanga, Zaire; Zambia; Maryland and California, USA and Seigen, Germany.
  • Best Field Indicators are crystal habit, streak, associations, tarnish and color.

 

 

 

 

THE MINERAL LIROCONITE

 

  • Chemistry: Cu2Al(AsO4)(OH)4 - 4H2O , Hydrated Copper Aluminum Arsenate Hydroxide.
  • Class: Phosphates
  • Subclass: Arsenates
  • Uses: Only as mineral specimens.
  • Specimens

Liroconite is a beautiful mineral that is not often available from any new sources. Fine crystal clusters were mined from the famous mines of Cornwall and Devon, England; the only site to produce significant specimens. But now that source is all but dried up although some of the old dumps have produced some specimens. Liroconite is found at other locations but only as traces. Collectors are almost completely relying on old collections to supply this mineral. Liroconite is a truly beautiful mineral with a typical bright blue color, a nice glassy luster and an interesting crystal habit. It forms from the oxidation of primary copper ores.

 

PHYSICAL CHARACTERISTICS:

  • Color is typically blue to bluish green.
  • Luster is vitreous.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include crusts with wedge to lens shaped crystals. Individual crystals can appear as if apart of the more symmetrical eight faced tetragonal bipyramid; but are actually composed of the faces of a four faced prism and four faces of two monoclinic domes.
  • Cleavage is poor in two directions parallel to the prism faces.
  • Fracture is uneven to conchoidal.
  • Hardness is 2 - 2.5.
  • Specific Gravity is approximately 2.95 - 3.00 (average for translucent minerals).
  • Streak is pale blue.
  • Other Characteristics: There is no reaction to acid as is true with azurite.
  • Associated Minerals are clinoclase, azurite, malachite, caledonite and linarite and other oxidation zone copper ore minerals.
  • Notable Occurrences include the famous mines of Cornwall and Devon, England such as the Wheal Gorland Mine; Russia; Germany; Cerro Gordo Mine, Inyo Co., California, USA and occasionally elsewhere.
  • Best Field Indicators are crystal habit, color, low density, non reaction to acids, associations and streak.

  

THE MINERAL LITHIOPHILITE

 

  • Chemistry: Li(Mn, Fe)PO4, Lithium Manganese Iron Phosphate.
  • Class: Phosphates
  • Uses: As a source of lithium and phosphorus and as mineral specimens.
  • Specimens

Lithiophilite, which is sometimes spelled lithiophylite, is a rather scarce phosphate mineral. The name can be loosely translated from the Greek as "lithium lover". Although it is scarce and generally does not form good crystals, it does have a wonderful although indirect benefit to the mineral world. Lithiophilite is a primary phosphate mineral found in phosphatic pegmatites and pegmatitic dikes. It alters easily into other phosphate minerals, especially manganese phosphates. These rare phosphate minerals are usually brightly colored and make wonderful mineral specimens. Some mines have been made famous by their suites of unusual and beautiful secondary phosphate minerals such as eosphorite, reddingite, sicklerite, hureaulite, fairfieldite, dickinsonite, stewartite, vivianite, salmonsite, strengite, purpurite, heterosite, phosphoferrite, wolfeite, triploidite and fillowite to name a few. And where did these phosphates come from? They are the products of the alteration and/or weathering of lithiophilite, triphylite, amblygonite and a few other primary phosphate minerals. This fact makes lithiophilite an appreciated mineral.

Lithiophilite forms a solid solution with the often associated mineral triphylite. Triphylite's formula is Li(Fe, Mn)PO4 and differs from lithiophilite by being rich in iron instead of manganese. The structures of the two minerals are the same and therefore any differences in physical properties between the two would be related to the iron/manganese percentage.

Lithiophilite is slightly less dense and is pinkish to greenish brown whereas triphylite's color tends toward blue and blue gray.

 

PHYSICAL CHARACTERISTICS:

  • Color is pinkish to greenish brown.
  • Luster is vitreous.
  • Transparency: Specimens are transparent to translucent.
  • Crystal System is orthorhombic; 2/m 2/m 2/m
  • Crystal Habits do not include well formed crystals because most crystals are embedded and appear as compact, cleavage masses and intergrown crystal clumps.
  • Cleavage is near perfect in one direction (basal) and imperfect in two directions (prismatic). All cleavages are at right angles to each other.
  • Fracture is uneven.
  • Hardness is variable from 4 - 5
  • Specific Gravity is approximately 3.34 (above average), but increases with increased iron content.
  • Streak is white to grayish-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. Hyper-weathering produces a black stain of manganese oxides.
  • Associated Minerals include lepidolite, beryl, quartz, albite, triphylite, amblygonite, spodumene and various manganese oxides. Associated secondary phosphates include eosphorite, reddingite, sicklerite, salmonsite, strengite, purpurite, phosphoferrite, wolfeite, triploidite, hureaulite, fairfieldite, dickinsonite, stewartite, vivianite, heterosite and fillowite.
  • Notable Occurrences are widespread and include Verutrask, Sweden; Mangualde, Portugal; Bavaria, Germany; Buckfield, Poland; Karidid District, Namibia; Namaqualand, South Africa; the Buranga pegmatite, Rwanda; Yellowknife, Northwest Territories, Canada; Rajasthan, India; Rio Grande do Norte, Brazil and Pilbara District, Australia. In the United States localities include Pala District of San Diego County, California; Newry, Stoneham and Topsham, Maine; Palermo Quarry, North Groton, New Hampshire; Custer, South Dakota and Branchville, Fairfield County, Connecticut.
  • Best Field Indicators are color, associations, environment, cleavage and density.

 

 

 

 THE MINERAL LOLLINGITE

 


Lollingite, or as it is alternatively spelled loellingite, is an uncommon mineral, but is found with other arsenides and thus it is included with them when mined for arsenic. It is often associated with arsenopyrite, FeAsS, and this is unfortunate as it is difficult to distinguish between the two. Their crystal forms, color, luster, streak and fracture are all very similar. Lollingite is at least somewhat softer and denser. Lollingite's composition is never exactly FeAs2, because it usually contains significant percentages of cobalt and nickel and sometimes sulfur.

Lollingite gives its name to a group of minerals of which the mineral lollingite is one of the more common members. Members of the Lollingite Group have a simple formula, namely: AX2. Where the metal ion, A, is either cobalt, nickel and/or iron and the X can be either arsenic and/or antimony with some members having some sulfur. All members of the group have lollingite's basic structure. They are all orthorhombic in symmetry and are very uncommon to rare in occurrence. Some classification schemes place Lollingite Group members in the Marcasite Group.

These are the members of the Lollingite Group:
  • Costilbite (Cobalt Antimonide Sulfide)
  • Lollingite (Iron Arsenide)
  • Nisbite (Nickel Antimonide)
  • Rammelsbergite (Nickel Arsenide)
  • Safflorite (Cobalt Iron Arsenide)
  • Seinajokite (Iron Nickel Antimonide Arsenide)

THE PHYSICAL CHARACTERISTICS OF LOLLINGITE:

  • Color is silver white to gray (tarnishes to a darker color).
  • Luster is metallic.
  • Transparency: Crystals are opaque.
  • Crystal System is Orthorhombic; 2/m 2/m 2/m
  • Crystal Habits include prismatic to stubby crystals with a chisel-like domal termination. A crystal's cross-section will be diamond-shaped with rounded oblique angles. Elongated wedge shaped crystals are seen when the domal termination becomes dominant. Also compact, massive and disseminated in veins fillings. Twins are seen as star shaped trillings.
  • Cleavage is indistinct (basal).
  • Fracture: Uneven.
  • Hardness is 5 - 5.5
  • Specific Gravity is approximately 7.1 - 7.5 (well above average for metallic minerals)
  • Streak is a gray black.
  • Other Characteristics: Crystals are commonly striated lengthwise.
  • Associated Minerals include arsenopyrite, pyrrhotite, chalcopyrite, biotite, analcime, sodalite, vesuvianite, calcite and siderite.
  • Notable Occurrences include Lolling (hence the name), Huttenburg, Carinthia, Austria; Harz, Germany; Franklin, New Jersey; Cobalt, Connecticut; Gunnison Co., Colorado; Alexander Co., North Carolina and Arizona, USA; Ontario, Canada; Norway; Sweden; Finland; Czech Republic; Poland and Brazil.
  • Best Field Indicators are crystal habits, color, associations, streak, hardness, striations and density.



 

 

THE MINERAL LORENZENITE

 


Lorenzenite is a rare mineral that was only discribed in the last 50 years. It is found on both the coast of Greenland and on the Kola Pennisula from where many new and rare minerals have been and are still being discovered. Ramsayite is the old russian name for lorezenite. Now the name Ramsayite is a synonym for lorenzenite. Lorenzenite has a rather high luster which is due to the titanium content. Other titanium minerals also have high lusters especially the mineral rutile, TiO2.

 

PHYSICAL CHARACTERISTICS:

  • Color is a brown, yellow-brown to dark brown.
  • Luster is vitreous to submetallic.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is Orthorhombic.
  • Crystal Habit is prismatic with six sides, two of the sides are often flattened to form a nearly tabular crystal with a pointed termination.
  • Hardness is 6.
  • Specific Gravity is approximately 3.4+ (above average for translucent minerals)
  • Streak is light brown.
  • Notable Occurrences: Narsarsuk, Greenland and Kola Pennisula, Russia.
  • Best Field Indicators are color, luster, density and locallity.



 

LORIMAR, the blue variety of pectolite

 

VARIETY INFORMATION:

  • VARIETY OF: Pectolite, NaCa2Si3O8(OH), Sodium Calcium Silicate Hydroxide.
  • USES: ornamental stone and semi-precious stone.
  • COLOR: pale blue to sky blue.
  • HARDNESS: 5
  • CLEAVAGE: perfect in two directions, but not seen in this compact form.
  • CRYSTAL SYSTEM: triclinic
  • Specimens

This variety is actually a rock, being composed of more than one mineral, but is mostly composed of pectolite. It has been given the trade name "Lorimar". Only discovered in the Bahamas and Dominican Republic in the last twenty years, it has enjoyed success in the semi-precious stone market. Its translucent, sky blue color is attractive and has a loyal following of admirers. It has a turquoise look to it, although the color is distinctly more blue. Lorimar has been used in the same manner as turquoise and is even seen in contemporary Native American jewelry. It has been quite versatile in its applications to other jewelry varieties. Lorimar offers a different color to those who like polished stone jewelry.

 

   

THE MINERAL LUDLAMITE

 

  • Chemistry: (Fe, Mg, Mn)3(PO4)2 - 4H2O, Hydrated Iron Magnesium Manganese Phosphate.
  • Class: Phosphates
  • Uses: Only as mineral specimens.
  • Specimens

Ludlamite is a classic phosphate mineral. Known from only a few localities, it is most famous from the classic Wheal Jane Mine in Cornwall, England. It was first discovered there (1876 - 1877) after the old mine had been reopened. The mine was closed for a long time until recently reopened in the past three decades and was again producing some ludlamite specimens. Ludlamite is named for Henry Ludlam, a British collector of fine rare minerals.

Specimens of ludlamite are extremely beautiful. They are characterized by a bright green, usually apple green color, a vitreous luster and an interesting crystal habit. The aggregates typically form into sprays of jaggedly pointed sheaves that are pinched in the middle like sheaves of wheat. To own a specimen is truly a blessing for a mineral collector.

 

PHYSICAL CHARACTERISTICS:

  • Colors include a few shades of green, often bright apple green or colorless.
  • Luster is vitreous.
  • Transparency: Specimens are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include tabular almost pseudo-octahedral crystals also as jagged, crystalline masses and aggregate sprays or sheaves.
  • Cleavage is perfect in one direction (basal).
  • Fracture is uneven.
  • Hardness is 3 - 4.
  • Specific Gravity is approximately 3.1 - 3.2 (very slightly above average).
  • Streak is white.
  • Associated Minerals include pyrite, limonite, siderite, triphylite, vivianite and other primary and secondary phosphates.
  • Notable Occurrences include Wheal Jane Mine, Truro, Cornwall, England; la Union, Spain; Rapid Creek, Yukon, Territory, Canada; Chihuahua, Mexico; Hagendorf, Germany; Cobalt, Idaho; North Groton, New Hampshire and Custer County, South Dakota, USA.
  • Best Field Indicators are crystal habit, color, locality and cleavage.

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