igneous
Quartz Vein in Rhyolite
Silicon Dioxide (SiO2) in extrusive igneous rock
Hardness: 7 (Quartz) and 6 (Rhyolite). Color: White to pale green quartz vein, purplish-gray host rock. Luster: Vitreous quartz, earthy/dull rhyolite. Crystal structure: Hexagonal (quartz), fine-grained aphanitic (rhyolite). Cleavage: None.
- Hardness
- 7 (Quartz) and 6 (Rhyolite)
- Color
- White to pale green quartz vein, purplish-gray host rock
- Luster
- Vitreous quartz, earthy/dull rhyolite
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Physical properties
Hardness: 7 (Quartz) and 6 (Rhyolite). Color: White to pale green quartz vein, purplish-gray host rock. Luster: Vitreous quartz, earthy/dull rhyolite. Crystal structure: Hexagonal (quartz), fine-grained aphanitic (rhyolite). Cleavage: None.
Formation & geological history
Formed when hydrothermal fluids rich in silica circulated through fractures in cooling volcanic rhyolite flows, precipitating mineral crystals as they cooled and pressurized. Often Precambrian to Tertiary in age.
Uses & applications
Used primarily as decorative garden stone or architectural fill. High-purity quartz veins are mined for industrial silicon or glass-making, while the host rock is used as crushed stone for aggregate.
Geological facts
Quartz veins are the primary targets for gold prospecting, as gold often precipitates with the silica in hydrothermal systems. This specimen shows a distinct 'ribbon' texture where the fracture opened multiple times.
Field identification & locations
Identify by the white 'seam' cutting through the host rock; quartz will scratch glass while many other minerals will not. Commonly found in volcanic belts, volcanic mountainous regions, and ancient lava fields.
