mineral

Arsenopyrite

Arsenopyrite (FeAsS)

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

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

Identified June 28, 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 (pseudo-orthorhombic); Cleavage: Distinct; Specific Gravity: 5.9-6.2.

Formation & geological history

Formed in high-temperature hydrothermal veins, contact metamorphic deposits, and pegmatites. It is often found in association with gold and other sulfide minerals.

Uses & applications

Primary ore of arsenic; historically used in insecticides, pigments, and glassmaking. Also an important indicator of gold mineralisation in mining exploration.

Geological facts

When struck with a hammer, it releases an unmistakable garlic-like odor due to the arsenic content. It is the most common arsenic-bearing mineral on Earth.

Field identification & locations

Identify by its silver color, high density, and garlic-like smell when crushed or heated. Common in mining districts like Cornwall (UK), Canada, and China. Collectors should handle with care and wash hands after touching.