ARSENOPYRITE MINERAL FACTS Nevada Turquoise gem stones
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.Arsenopyrite Mineral Facts:

Chemical Formula: FeAsS  - 46% Arsenic by weight

Colors: Silver to steel gray in color. Streak is black.

Hardness: 5.5 to 6

Density: 6 to 6.2
The density is high because of the large silver content. 

Cleavage: No cleavage but the mineral is brittle and its fracture uneven.

Crystallography: Orthorhombic
Usually in tabular diamond shaped crystals, formed by a short prism terminated by low brachydomes.
Twinned at times, giving stellate groups.

Luster:. Metallic luster.

Optics: (Refractive Index):  Opaque

Composition, Structure and Associated Minerals:
Arsenopyrite, or mispickel, is the most important ore of arsenic.  It is found in crystals and in compact and granular masses. It is a silver-white metallic mineral resembling very closely cobaltite in its general appearance. In many specimens the iron is replaced in part by cobalt, nickel or manganese. Sometimes the cobalt is present in such large quantity that the mineral is smelted as an ore of this metal. Arsenopyrite is the most common mineral containing arsenic. Found in veins in crystalline rocks, associated with ores of tin, silver, lead and with various sulfides , including pyrite, chalcopyrite, sphalerite, galena, etc. Sometimes it is auriferous and serves as a gold ore.

Identification and Diagnostics
Recognized usually by its silver-white color, its crystals and a test for arsenic. The mineral yields sparks when struck with steel and emits an arsenic smell. It dissolves in nitric acid with the separation of sulfur. Arsenopyrite is distinguished from the cobalt sulfides and arsenides by the absence of large amounts of cobalt.  Fusible at 2 to a magnetic globule. B. B. on charcoal gives a volatile coating of arsenious oxide and a characteristic garlic odor. In 0. T. gives odor of sulfur dioxide and a volatile ring of arsenious oxide. In C. T. gives arsenic mirror. It is a good conductor of electricity.

Occurrence, Localities and Origins:
Occurrence. Arsenopyrite crystals are often found disseminated through crystalline rocks, and often embedded in the gangue minerals of veins. Like pyrite and marcasite they frequently fill vein  fissures. Its associates are silver, tin and lead ores, chalcopyrite, pyrite and sphalerite. The mineral is abundant at Freiberg, in Saxony, at Tunaberg, in Sweden, and at Inquisivi Mt., Sorato, in Bolivia; with tin ores in Cornwall, England; New South Wales and Deloro, Canada, where it is mined as a gold ore. It also occurs in fine crystals at Franconia in New Hampshire, at Blue Hill in Maine, at Chatham in Connecticut, and at St. Francois, Beauce Co., Quebec. Massive arsenopyrite is found near Keeseville Essex Co., near Edenville, Orange Co., and near Carniel, Putnam Co., N. Y., and at Rewald, Floyd Co.., Va. In most cases it is apparently a result of pneumatolysis.

Arsenopyrite was formerly the source of nearly all the arsenic of commerce. The mineral is concentrated by mechanical methods, and the concentrates are heated in retorts. When the mineral contains a reasonable amount of cobalt or of gold these metals are extracted. The metal arsenic has very little use in the arts, though its compounds find many applications as insecticides, medicines, pigments, in tanning, etc.

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Arsenopyrite Crystals

Arsenopyrite, small crystals



Please note that the author, Chris Ralph, retains all copyrights to this entire document and it may not be reproduced, quoted or copied without permission.

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