sedimentary
Pyrite in Shale
Iron Sulfide (FeS2) in Argillaceous Shale
Hardness: 6-6.5 (Pyrite) / 3 (Shale); Color: Brass-yellow (Pyrite) on Grey/Black (Shale); Luster: Metallic; Crystal Structure: Isometric/Cubic crystals embedded in a fine-grained matrix; Streak: Greenish-black
- Hardness
- 6-6
- Color
- Brass-yellow (Pyrite) on Grey/Black (Shale)
- Luster
- Metallic
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Physical properties
Hardness: 6-6.5 (Pyrite) / 3 (Shale); Color: Brass-yellow (Pyrite) on Grey/Black (Shale); Luster: Metallic; Crystal Structure: Isometric/Cubic crystals embedded in a fine-grained matrix; Streak: Greenish-black
Formation & geological history
Formed in low-oxygen (anoxic) sedimentary environments where organic matter and sulfates are present. Microbiological activity reduces sulfate to sulfide, which reacts with iron to form pyrite crystals within the settling mud that later lithifies into shale.
Uses & applications
Pyrite is used as a source of sulfur and in the production of sulfuric acid. In this specific form, it is primarily a geological specimen for education or collecting.
Geological facts
Pyrite is known as 'Fool\'s Gold' because of its metallic luster and yellow hue. When found in shale, it often indicates the presence of organic-rich prehistoric mudflats or deep-ocean floors.
Field identification & locations
Identify by looking for metallic, cubic glints against a dull, grey, flaky rock. Use a hand lens to see the sharp crystal edges. Commonly found in sedimentary basins and coal beds.
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