metamorphic
Quartzite Pebble with Pyrite Coating
SiO2 (Quartz) with FeS2 (Pyrite) inclusions or surface coating
Hardness: 7 for quartz core, 6-6.5 for pyrite coating. Color: Milky white to tan with a metallic greenish-brass/golden coating. Luster: Vitreous to dull on the stone body, metallic on the coated section. Specific Gravity: ~2.65 - 5.0 depending on pyrite ratio.
- Hardness
- 7 for quartz core, 6-6
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Physical properties
Hardness: 7 for quartz core, 6-6.5 for pyrite coating. Color: Milky white to tan with a metallic greenish-brass/golden coating. Luster: Vitreous to dull on the stone body, metallic on the coated section. Specific Gravity: ~2.65 - 5.0 depending on pyrite ratio.
Formation & geological history
Formed via regional metamorphism of quartz sandstone, creating a dense quartzite matrix. The metallic exterior crust forms from iron and sulfur-rich hydrothermal fluids depositing fine pyrite or marcasite micro-crystals on the rock surface.
Uses & applications
Mainly collected as a curious geological specimen, decorative stone, or river pebble collectible.
Geological facts
Pyrite coatings on river-worn quartz pebbles often occur in micro-reducing environments in streams rich in iron and organic material, creating a distinctive metallic shell over smooth white quartz.
Field identification & locations
Identified by the rounded, hard quartz body partially coated with fine, sparkling metallic micro-grains that show a brassy/greenish tint. Commonly found in gravel beds, stream deposits, and glacial drift.
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