mineral

Pyrite in Shale

Iron Sulfide (FeS2) in Sedimentary Matrix

AI-generated identification · may be incorrect

Hardness: 6-6.5 (Pyrite), 2-3 (Shale mask); Color: Brass-yellow (mineral), Charcoal gray (matrix); Luster: Metallic; Crystal Structure: Isometric/Cubic; Cleavage: Indistinct; Specific Gravity: 4.8-5.0

Hardness: 6-6
Color: Brass-yellow (mineral), Charcoal gray (matrix)
Luster: Metallic

Identified April 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed in anoxic (oxygen-poor) sedimentary environments through the interaction of iron and hydrogen sulfide generated by sulfate-reducing bacteria. Commonly found in organic-rich shales or coal beds.

Uses & applications

Source of sulfur and iron (historically); widely used as a decorative collector's specimen and in jewelry (often incorrectly called 'marcasite').

Geological facts

Known as 'Fool's Gold' because its metallic luster and brassy color resemble real gold, though it is much harder and more brittle. It can spark when struck against steel.

Field identification & locations

Identify by its golden-metallic color against dark rock, crystalline shape, and brassy streak. It will scratch glass, unlike gold. Common in mining regions worldwide.