mineral

Tumbled dark sulfide-rich mineral specimen (possibly pyrite/marcasite)

Tentatively iron disulfide, FeS₂; exact identification requires testing

AI-generated identification · may be incorrect

Dark gray-brown, metallic to submetallic luster with irregular crystalline surfaces; likely hardness about 6–6.5 if pyrite, lower and more brittle if marcasite. Specific gravity is approximately 4.8–5.0; crystal structure cannot be confirmed from the image.

Identified August 24, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed in hydrothermal veins or sedimentary rocks through precipitation of iron sulfides, commonly during the Paleozoic–Mesozoic or younger geological episodes.

Uses & applications

Collected as a mineral specimen; pyrite is used historically as a sulfur source and occasionally for decorative objects, but this small piece has little industrial value.

Geological facts

Pyrite is commonly called “fool’s gold,” though this specimen appears unusually dark and may be weathered or coated. Marcasite can chemically alter to powdery iron sulfate in humid conditions.

Field identification & locations

Common localities include Peru, Spain, Italy, China, and the United States. Check for a black-green streak, metallic sheen, high density, and sparks when struck; a streak and hardness test can distinguish it from galena or hematite.