mineral

Arsenopyrite in Quartz Matrix

Arsenopyrite (FeAsS) with Quartz (SiO2)

Hardness: 5.5-6 (arsenopyrite) and 7 (quartz). Color: Tin-white to steel-gray metallic crystals embedded in white-to-tan matrix. Luster: Metallic (sulfide) and Vitreous (quartz). Crystal Structure: Monoclinic/Prismatic. Specific Gravity: 5.9-6.2 for the sulfide parts.

Hardness: 5
Luster: Metallic (sulfide) and Vitreous (quartz)

Identified March 1, 2026More mineral →

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Physical properties

Formation & geological history

Formed in high-temperature hydrothermal veins, frequently associated with gold-bearing quartz systems. Often found in metamorphic rocks or near igneous intrusions where sulfur-rich fluids circulate.

Uses & applications

Primary ore of arsenic; historically used in pigments, pesticides, and glass manufacturing. Also collected as a mineral specimen and acts as an indicator mineral for gold prospecting.

Geological facts

When struck with a hammer, arsenopyrite emits a distinct garlic-like odor due to the release of arsenic vapors. It is the most common arsenic-bearing mineral on Earth.

Field identification & locations

Identify by its heavy weight, metallic gray color, and garlic smell when crushed. Commonly found in mining districts like Cornwall, UK, and the Sierra Nevada, USA. Collectors should handle with care and wash hands after touching due to arsenic content.

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