mineral

Likely iron sulfide specimen (pyrite or marcasite)

Pyrite, FeS₂; possibly marcasite, also FeS₂

AI-generated identification · may be incorrect

Brassy yellow to bronze metallic luster, granular/irregular texture, and relatively high density; pyrite hardness is 6–6.5 Mohs, while marcasite is softer at about 6–6.5. The photograph cannot reliably distinguish the two or confirm crystal form.

Identified August 19, 2026More mineral →

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Physical properties

Formation & geological history

Forms in sulfur- and iron-rich hydrothermal veins, sedimentary rocks, and metamorphic settings; individual specimens may range from modern weathering products to Precambrian or younger deposits. The surrounding dark material may be host rock or weathered sulfide matrix.

Uses & applications

Pyrite is collected, used historically as a sulfur source, and studied as an ore indicator; it has limited jewelry use because it tarnishes and can oxidize. Marcasite has been used in ornamental jewelry but is unstable in humid conditions.

Geological facts

Pyrite is nicknamed “fool’s gold,” but it is harder and more brittle than gold and commonly leaves a dark greenish-black streak rather than a yellow one. Marcasite can decay into acidic iron sulfate minerals.

Field identification & locations

Check for metallic luster, heavy weight, brittle fracture, and a dark streak; avoid tasting or prolonged skin contact with unknown sulfides. Common localities include Peru, Spain, Italy, China, the United States, and Canada.