metamorphic
Quartz-Veined Gneiss or Metamorphic Rock with Quartz Veins
Quartz-veined metamorphic rock (Silicate mineral assemblage)
Hardness: 7 (for quartz veins), 5-6 (for host rock); Color: Dark grey to black with white and yellowish quartz banding; Luster: Vitreous on quartz veins, dull to greasy on host rock; Structure: Foliated with discordant hydrothermal veins; Specific Gravity: ~2.6 - 2.8
- Hardness
- 7 (for quartz veins), 5-6 (for host rock)
- Color
- Dark grey to black with white and yellowish quartz banding
- Luster
- Vitreous on quartz veins, dull to greasy on host rock
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Physical properties
Hardness: 7 (for quartz veins), 5-6 (for host rock); Color: Dark grey to black with white and yellowish quartz banding; Luster: Vitreous on quartz veins, dull to greasy on host rock; Structure: Foliated with discordant hydrothermal veins; Specific Gravity: ~2.6 - 2.8
Formation & geological history
Formed through regional metamorphism of pre-existing protoliths under high temperature and pressure, subsequently fractured and hydrothermally injected with silica-rich fluids that crystallized into quartz veins.
Uses & applications
Used primarily as decorative landscape gravel, in construction aggregate, or as a geological specimen for collectors.
Geological facts
Quartz veins form when mineral-rich water circulates through fractures in the Earth's crust under high pressure and temperature, depositing dissolved silica as solid quartz.
Field identification & locations
Can be identified in the field by contrasting alternating dark metamorphic bands cut across sharply by bright white or yellowish quartz veins. Common in ancient shields, mountain belts, and river gravels.
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