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Chemical Formula | FeAsS | ||
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Composition | Iron arsenic sulfide, sometimes with some cobalt | ||
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Variable Formula | (Fe,Co)AsS | ||
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Color | Silver-white to steel-gray. Tarnishes dark gray, but occasionally also an iridescent pink and yellow. | ||
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Streak | Grayish-black | ||
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Hardness | 5½ - 6 | ||
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Crystal Forms and Aggregates |
(Monoclinic) [Arsenopyrite was previously
thought to be orthorhombic, but recent analysis proves it
as monoclinic] Occurs as distinct prismatic crystals, which are often twinned and striated. Twins may form interesting crosses and stars. Also occurs as elongated crystals, columnar, grainy, massive, as veins, in compact crystal groups, and massive. |
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Transparency | Opaque | ||
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Specific Gravity | 5.9 - 6.2 | ||
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Luster | Metallic | ||
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Cleavage | 2,1 - prismatic | ||
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Fracture | Uneven | ||
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Tenacity | Brittle | ||
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Other ID Marks | 1) Gives off a garlic odor when struck or
heated (Warning: Do not heat. Fumes are
toxic) 2) Triboluminescent |
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Other Names |  Arsenical Pyrites,  Mispickel |
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Varieties | Danaite - Cobalt-rich variety, in which
the cobalt may replace as much as 12 percent of the iron. A mineral very similar to Arsenopyrite, Gudmundite, is sometimes wrongly classified as a variety of Arsenopyrite. |
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In Group | Sulfides ; Simple sulfides (May also be classified as a sulfosalt, since it is composed of sulfur and arsenic) |
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Uses | Arsenopyrite is the most prevalent mineral
containing arsenic, and is thus a major ore
of that element. It is also a minor ore of gold,
containing traces of gold in some localities. Arsenopyrite is famous for its distinctive crystals, and is a popular mineral among mineral collectors. |
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Striking Features | Crystal habits, gives off garlic odor when struck | ||
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Complex Tests | Dissolves in nitric acid | ||
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Popularity (1-4) | 2 | ||
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Prevalence (1-3) | 2 | ||
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Demand (1-3) | 1 | ||
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Distinguishing Similar Minerals |
Pyrite, Marcasite, and Pyrhottite -
occur in different crystals, more yellow in color Loellingite - very hard to distinguish, but lacks the sulfur attributes of Arsenopyrite Cobaltite - occurs in different crystals |
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Commonly Occurs With |
Quartz, Pyrite, Chalcopyrite, Pyrrhotite, Gold, Silver, Siderite, Garnet, Muscovite, Orthoclase | ||
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Noteworthy Localities |
Some of the best examples of Arsenopyrite
are from Panasqueira, Portugal. Excellent crystals also
come from Potosi, Bolivia; Freiberg, Germany; Cornwall,
England; Trepca, former Yugoslavia; and Iname, Aichi
Prefecture, Japan. Long, acicular crystals were found in
the Obira Mine on Kyushu Island, Japan. Fine Arsenopyrite has also come from Mexico in Mapimi, Durango. In Canada, it occurs in Cobalt; Timiskaming District, Ontario and in the Nickel Plate Mine, British Columbia. In the U.S., localities include Mount Mica, Oxford Co., Maine; Roxbury, Litchfield Co., Connecticut; Lewis, Essex Co., New York; Leadville, Lake Co., Colorado; the Haynes-Stellite mine, Blackbird district, Lemhi Co., Idaho; and the Cleveland mine, Stevens Co., Washington. Fine specimens were once found Carmel, Putnam Co., New York. Much Arsenopyrite has also come from the gold-producing regions in the Sierra Nevada Mountains of California, namely in the Monitor-Mogule District. The cobalt-rich variety, Danaite, comes from Franconia, Grafton Co., New Hampshire. |
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Picture Icon Links |
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Picture Links | 1. Arsenopyrite with Quartz |
