metamorphic
Quartz Vein in Host Rock (Likely Slate or Shale)
Hydrothermal Quartz (SiO2) in Pelitic host rock
Hardness: 7 (Quartz) vs 3-4 (Host); Color: Milky white and dark grey; Luster: Vitreous to dull; Crystal structure: Trigonal (Quartz); Cleavage: None (conchoidal fracture in quartz)
- Hardness
- 7 (Quartz) vs 3-4 (Host)
- Color
- Milky white and dark grey
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Quartz) vs 3-4 (Host); Color: Milky white and dark grey; Luster: Vitreous to dull; Crystal structure: Trigonal (Quartz); Cleavage: None (conchoidal fracture in quartz)
Formation & geological history
Formed via hydrothermal activity where mineral-rich hot water injected into fractures of existing sedimentary or metamorphic rock during tectonic mountain building. Most veins occur in Paleozoic or older formations.
Uses & applications
Used for architectural aggregate, source for high-purity silica, and as an indicator for precious metal prospecting (like gold found in quartz veins).
Geological facts
Quartz veins are often the 'fingerprints' of ancient geological movements. In many regions, these veins are the primary source of 'lode' gold, which is freed when the rock weathers away into riverbeds.
Field identification & locations
Identify in the field by the sharp contrast between the white, translucent quartz and the dark, fine-grained host rock. It will easily scratch glass. Commonly found in road cuts or mountain streams.
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