mineral

Arsenopyrite in Sulphide Ore

Arsenopyrite (FeAsS)

Hardness: 5.5-6.0 Mohs; Color: Silver-white to steel gray; Luster: Metallic; Crystal Structure: Monoclinic; Cleavage: Distinct; Specific Gravity: 5.9-6.2

Hardness: 5
Color: Silver-white to steel gray
Luster: Metallic

Identified June 4, 2026More mineral →

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Physical properties

Hardness: 5.5-6.0 Mohs; Color: Silver-white to steel gray; Luster: Metallic; Crystal Structure: Monoclinic; Cleavage: Distinct; Specific Gravity: 5.9-6.2

Formation & geological history

Formed in high-temperature hydrothermal veins, pegmatites, and contact metamorphic deposits. Often found associated with gold, silver, and copper ores.

Uses & applications

Primary ore of arsenic; used in lead alloys, semiconductors, glass making, and historical pigments. Collectors value well-crystallized specimens.

Geological facts

When struck with a hammer or heated, it emits a strong, garlic-like odor due to the release of arsenic vapors. It is the most common arsenic-bearing mineral.

Field identification & locations

Identify by its metallic silver luster, high density (heavy for its size), and garlic-like smell when crushed. Commonly found in mining districts of Cornwall, Germany, and Canada.