mineral
Pyrite in Shale
Iron Sulfide (FeS2) in Sedimentary Matrix
AI-generated identification · may be incorrectHardness: 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
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Physical properties
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
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.
