mineral

Arsenopyrite with Quartz

Arsenopyrite (FeAsS)

Hardness: 5.5 to 6 on Mohs scale; Color: Silver-white to steel-gray; Luster: Metallic; Crystal Structure: Monoclinic (often occurring in prismatic crystals or tabular forms); Cleavage: Distinct; Specific Gravity: 5.9–6.2. Often associated with translucent quartz crystals.

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

Identified March 20, 2026More mineral →

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Physical properties

Formation & geological history

Formed in high-temperature hydrothermal veins, often alongside gold, silver, and copper ores. It can also occur in contact metamorphic environments and pegmatites. It is the most common arsenic-bearing mineral.

Uses & applications

Primary source of arsenic for industrial use, including pesticides, herbicides, and wood preservatives. It is also significant in gold mining as it is often a 'pathfinder' mineral for gold deposits.

Geological facts

When struck with a hammer, it emits a distinct garlic-like odor due to the release of arsenic vapors. Its name is a contraction of 'arsenical pyrites'. While it contains iron like pyrite, it is much denser and has a different crystal habit.

Field identification & locations

Identify in the field by its high density, metallic silver luster, and the garlic smell when crushed or heated. It's commonly found in Germany, China, Portugal, and Canada. Collectors value sharp, well-defined crystals over massive forms.