metamorphic
Quartzite
Hydrothermal Quartz or Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or milky white with iron staining; Luster: Vitreous to waxy; Crystal structure: Hexagonal cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: ~2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or milky white with iron staining
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or milky white with iron staining; Luster: Vitreous to waxy; Crystal structure: Hexagonal cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: ~2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone or through the deposition of silica from hydrothermal fluids in veins. This specimen shows significant water-wear and rounding typical of river or stream transport.
Uses & applications
Used as a decorative stone in landscaping, crushed for road construction base, or as a source of silica in glass manufacturing. Some smooth specimens are used as 'worry stones' or for lapidary tumbling.
Geological facts
Quartz is one of the most chemically and physically resistant minerals on Earth's surface, which is why it commonly persists as pebbles in riverbeds long after other minerals have weathered away.
Field identification & locations
Identify in the field by its hardness (it should easily scratch glass) and its lack of internal grains compared to sandstone. Look for the smooth, 'frosted' surface texture and conchoidal fracture scars along edges.
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