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Arsenopyrite Individual Crystals

The Mineral arsenopyrite




Arsenopyrite is the most prevalent mineral containing the element arsenic. It forms very distinct crystals which can be large and beautifully formed, and it is a popular collectors mineral. It sometimes tarnishes and forms an iridescent layer.
Chemical Formula FeAsS
Composition Iron arsenic sulfide, sometimes with some cobalt
Variable Formula (Fe,Co)AsS
Color Silver-white to steel-gray. Tarnishes dark gray, but occasionally also an iridescent pink and yellow.
Streak Grayish-black
Hardness 5.5 - 6.5
Crystal System Monoclinic
3D Crystal Atlas
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Crystal Forms
and Aggregates
Arsenopyrite was previously thought to crystallize in the orthorhombic system, but recent analysis has proved it to be monoclinic. It occurs as distinct prismatic crystals, which are often twinned and striated and triangular in shape. Twins may form interesting crosses and stars. Also occurs as elongated crystals, columnar, grainy, massive, as veins, and in compact crystal groups.
Transparency Opaque
Specific Gravity 5.9 - 6.2
Luster Metallic
Cleavage 2,1 - prismatic
Fracture Uneven
Tenacity Brittle
Other ID Marks 1) Gives off a garlic odor when struck or heated.
2) Triboluminescent.
Complex Tests Dissolves in nitric acid
In Group Sulfides; Simple Sulfides
Striking Features Crystal habits, gives off garlic odor when struck
Environment High temperature ore veins, pegmatites, and contact metamorphic rocks. Rarely in igneous basalt rocks.
Rock Type Igneous, Sedimentary, Metamorphic
Popularity (1-4) 2
Prevalence (1-3) 2
Demand (1-3) 1

Arsenopyrite ON EBAY
OTHER NAMES
Arsenical Pyrites
Mispickel

VARIETIES
 -  Cobaltrich variety of Arsenopyrite, in which the cobalt may replace as much as 12 percent of the iron. Found in Franconia, New Hampshire.
 -  Mineral almost identical to Arsenopyrite, but contains antimony in place of the arsenic. Its chemical formula is FeSbS. Gudmundite is very similar in physical properties to Arsenopyrite, and is sometimes wrongly classified as a variety of it, when in fact it is scientifically a separate mineral species. It is found in Gudmundstorp, Sala, Sweden and in Ilimaussaq, Greenland.

USES
Arsenopyrite is a major ore of the element arsenic. It is also a minor ore of gold, being that it contains traces of gold in some localities.

NOTEWORTHY LOCALITIES
Some of the best examples of Arsenopyrite are from Panasqueira, Portugal; and the Yaogangxian Mine, Hunan Province, China. Excellent crystals also come from the Huanggang Mine, Inner Mongolia, China; the Obira Mine on Kyushu Island, Japan; Freiberg, Saxony, Germany; the Cornwall area, England; Trepca, Kosovo (former Yugoslavia); Potosi, Bolivia; the Pachapaqui District, Ancash Dept., Peru.

Fine Arsenopyrite has also come from Mexico in several important localities, specifically Santa Eulalia, Chihuahua; and Concepcion del Oro, Zacatecas. 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; Franklin, Sussex Co., New Jersey; Leadville, Lake Co., Colorado; and the Cleveland mine, Stevens Co., Washington. Fine specimens were once found Carmel, Putnam Co., New York. The cobalt-rich variety, Danaite, comes from Franconia, Grafton Co., New Hampshire.

COMMON MINERAL ASSOCIATIONS
Quartz, Pyrite, Chalcopyrite, Pyrrhotite, Gold, Silver, Siderite, Garnet, Muscovite, Orthoclase

DISTINGUISHING SIMILAR MINERALS
Pyrite, Marcasite, and Pyrrhotite - 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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