metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: White, cream, yellowish-tan; Luster: Vitreous to waxy; Structure: Granoblastic, microcrystalline quartz; Specific Gravity: 2.6–2.7
- Hardness
- 7 (Mohs scale)
- Color
- White, cream, yellowish-tan
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: White, cream, yellowish-tan; Luster: Vitreous to waxy; Structure: Granoblastic, microcrystalline quartz; Specific Gravity: 2.6–2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure Recrystallize the sand grains into a dense, interlocking matrix of quartz crystals. This specimen has been rounded by fluvial (river) or coastal water erosion.
Uses & applications
Commonly used as a construction aggregate, for railroad ballast, and in landscaping. Highly polished specimens are used as decorative pebbles or aquarium stones.
Geological facts
Quartzite is so tough that it often remains as resistant ridges or hilltops while surrounding softer rocks erode away. It is significantly harder than the sandstone from which it originates.
Field identification & locations
Identify in the field by its inability to be scratched by steel and its grainy, crystalline appearance. Commonly found along riverbanks, beaches, and in ancient glacial deposit areas.
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