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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. Arsenopyrite sometimes tarnishes, forming a colorful 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 indicates a monoclinic symmetry. Occurs as distinct prismatic crystals, which are often twinned 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. Crystals are usually striated.
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 AUCTIONS
Arsenical Pyrites

 -  Cobalt-rich 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 Ilimaussaq, Greenland.

Arsenopyrite is an important ore of the element arsenic. It is also a minor ore of gold, as it contains traces of gold in some localities. Well-formed, lustrous Arsenopyrite crytals are important collector specimens.

Arsenopyrite can be found worldwide, but crystals of good quality are more limited. Excellent specimens of Arsenopyrite are found in Asia at the Yaogangxian Mine, Hunan Province, China; the Huanggang Mine, Inner Mongolia, China; and the Obira Mine on Kyushu Island, Japan.

Important European localities for Arsenopyrite include Panasqueira, Portugal; Freiberg, Saxony, Germany; Trepca, Kosovo (former Yugoslavia); and several of the ore deposits in the Cornwall area in England. In South America, fine Arsenopyrite crystals have come from Potosi, Bolivia; and the Pachapaqui District, Ancash Dept., Peru. Mexico also contains several notable occurrences, especially the Santa Eulalia district, Chihuahua; and Concepcion del Oro, Zacatecas.

In the U.S., Arsenopyrite 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. In Canada, Arsenopyrite is found in the Cobalt area, Timiskaming District, Ontario; and in the Nickel Plate Mine, British Columbia.

Quartz, Pyrite, Chalcopyrite, Pyrrhotite, Gold, Silver, Siderite, Garnet, Muscovite, Orthoclase

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.

arsenopyrite PHOTOS
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