mineral

Arsenopyrite with Schist Matrix

Arsenopyrite (FeAsS)

Hardness: 5.5-6.0 on the Mohs scale; Color: Silver-white to steel-gray, often with a yellow tarnish; Luster: Metallic; Crystal Structure: Monoclinic; Cleavage: Distinct; Specific Gravity: 5.9-6.2

Hardness: 5
Color: Silver-white to steel-gray, often with a yellow tarnish
Luster: Metallic

Identified March 26, 2026More mineral →

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Physical properties

Hardness: 5.5-6.0 on the Mohs scale; Color: Silver-white to steel-gray, often with a yellow tarnish; 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 environments. Often associated with quartz and various ores through magmatic differentiation or metamorphic processes.

Uses & applications

Primary ore of arsenic; historically used in metallurgical processes, insecticides, and pigments. In the modern era, it is primarily a collector's mineral and a byproduct in gold mining.

Geological facts

When struck with a hammer, it releases a distinct, garlic-like odor which is a key identifying characteristic of arsenic-bearing minerals. It is the most common arsenic mineral found in the Earth's crust.

Field identification & locations

Identify in the field by its high density, metallic silver-gray streak, and garlic smell when crushed. Commonly found in metamorphic belts like the Appalachians, Alps, and Andes, or mining districts in China and Canada.

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