metamorphic
Gold-bearing Quartz Vein in Mafic Rock
Hydrothermal Quartz Vein within Greenschist/Amphibolite facies (SiO2 with Au)
Hardness: 7 (quartz) to 5-6 (host rock). Color: White, gray, dark green to black. Luster: Vitreous to dull. Structure: Crystalline quartz veins cutting through a microcrystalline mafic matrix. Cleavage: None in quartz; poor in matrix.
- Hardness
- 7 (quartz) to 5-6 (host rock)
- Color
- White, gray, dark green to black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (quartz) to 5-6 (host rock). Color: White, gray, dark green to black. Luster: Vitreous to dull. Structure: Crystalline quartz veins cutting through a microcrystalline mafic matrix. Cleavage: None in quartz; poor in matrix.
Formation & geological history
Formed through hydrothermal processes where hot, mineral-rich fluids circulate through fractures in deep oceanic or volcanic crustal rocks, depositing silica and sometimes precious metals during cooling or chemical changes.
Uses & applications
Primary source for hard-rock gold mining; ornamental specimen collecting; geological research into ore-forming processes.
Geological facts
Many of the world's most productive gold rushes, such as the California Gold Rush, began by finding 'lode' deposits exactly like this where quartz veins carry microscopic or visible gold.
Field identification & locations
Identify by looking for white quartz 'veins' or 'ribbons' cutting across darker, fine-grained host rocks. Often found in mountain belts and archaean greenstone belts (e.g., Canada, Australia, South Africa).
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