Arsenopyrite – Mispickel, Composition, Crystallization and Structure

Composition. Sulpharsenidec of iron, FeAsS = Arsenic 46, sulfur 19.7, iron 34.3. sometimes cobalt replaces a part of he iron (danaite).

Crystallization. Orthorhombic. Usually in tabular diamond shaped crystals, formed by a short prism terminated by low brachydomes. The brachydomes are usually striated parallel to the brashy-axis (Fig. 237). Twinned at times, giving stellate groups; the different individuals of the twin groups being distinguished from each other by the striations upon them. Aggress closey in angles and crystals habit with marasite.

Structure. In crystals. Massive, granular to compact.

Physical properties. H. = 5.5-6. G. = 6-6.2. Metallic luster. Silver-white color. Black streak

Tests. Fusible at 2 to a magnetic globe. B. B. on charcoal gives a volatile coating of arsenious oxide and a characteristic garlic odor. In O. T. gives odor of sulfur dioxide and a volatile ring of arsenious oxide. In C. T. gives arsenic mirror. Recognized usually by its silver- white color, its crystals and a test for arsenic.

Occurrence. Arsenopyrite the most common mineral containing arsenic. It occurs with tin and tungsten ores in pneumatolitic deposits. In veins formed by deposition from hot waters, associated with silver ores, galena, sphalerite, pyrite, chalcopyrite, etc. frequently associated with gold. At times it occurs disseminated in crystalline rocks, limestone, serpentine, etc. occurs in quantity at Freiberg and Munzing, Saxony,with tin ores in Cornawall, England; from Tavistock, Devonshire; in various places in Bolivia; Deloro, Ontario, Canada, where it is mined as a gold ore, Roxbury, Connecticut, etc.

Use. An ore of arsenic. Arsenious oxide is used in the manufacture of glass, as a poison and a preservative. Paris green, an arsenate and arsenate of copper, is used as a position and a pigment. Sulfides of arsenic are used for paints fireworks.

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