Mineralpedia Details for Arsenopyrite

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Arsenopyrite

Name is a combination of the old term “arsenical pyrites.” Silver white to steel grey, often tarnish giving an iridescence. Crystals short prismatic, often elongated parallel to c-axis. Uncommonly twinned as star-like trillings. Usually granular to massive. Arsenopyrite is the most abundant and widespread of the arsenic minerals and has thousands of worldwide localities, some of which have large and/or fine crystals and include Germany, Serbia, Portugal, Sweden, Greece, England, the United States, Mexico, Canada, Japan, and many others. Most commonly found in medium to high temperature veins. Common in metamorphic deposits, sparse in pegmatites.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/arsenopyrite.pdf

Formula: FeAsS
Crystal System: Monoclinic
Crystal Habit: Striated, Euhedral Crystals, Prismatic
Cleavage: one distinct
Luster: Metallic
Color: tin white, light steel gray
Streak: black
Geological Setting: Widespread. Most commonly found in medium to high temperature veins.
Class: Monoclinic - Prismatic
Fracture: Brittle
Hardness: 5.5 to 6
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Mindat: View Arsenopyrite

Arsenopyrite from Double Rainbow mine, Galena, Lawrence Co., South Dakota, United States

8mm replacements of Pyrrhotite.

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Arsenopyrite from Panasqueira, Covilha, Castelo Branco dist., Portugal

Large crystal clusters of highly reflective Arsenopyrite with crystals to over 5cm.

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Arsenopyrite from Hedley, Osoyoos Mining Division, British Columbia, Canada

Granular or massive steel grey or tin white Arsenopyrite from 5 to 10mm.

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Arsenopyrite from Obira mine, Ono-gun, Oita prefecture, Kyushu Region, Japan

Grey, dull, elongated, prismatic crystals to 5cm.

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Arsenopyrite from Pribram, Bohemia, Czech Republic

1.5cm Arsenopyrite crystals.

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Arsenopyrite from Mina Ojuela, Mapimi, Durango, Mexico

2-3mm crystals within vugs of Pyrite and Arsenopyrite matrix.

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Arsenopyrite from Quiruvilca mine, Santiago de Chuco prov., La Libertad dept., Peru

Very sharp short prismatic crystals to 3mm with wedge-shaped terminations and triangular faces. Some of the crystals are short enough to appear pseudo-octahedral.