metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: White, cream, or light grey; Luster: Vitreous to waxy when polished; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.63-2.65
- Hardness
- 7 (Mohs scale)
- Color
- White, cream, or light grey
- Luster
- Vitreous to waxy when polished
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Physical properties
Hardness: 7 (Mohs scale); Color: White, cream, or light grey; Luster: Vitreous to waxy when polished; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.63-2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together. The pebble shape indicates it was tumbled and rounded by water action in a river or beach environment.
Uses & applications
Used as decorative gravel in landscaping, as an abrasive in industry, as a building stone (when in large blocks), and occasionally for tumbled pocket stones or jewelry.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the peaks of mountain ranges. A quartzite pebble is usually stronger than the parent sandstone and will break across the original sand grains rather than around them.
Field identification & locations
Identify in the field by its hardness (it will easily scratch glass) and lack of reaction to acid. Look for rounded, smooth shapes in creek beds or shorelines. Very common worldwide.
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