metamorphic
Quartzite pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Tanish-yellow to light brown; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: approx 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- Tanish-yellow to light brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tanish-yellow to light brown; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: approx 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure causes recrystallization of the quartz grains, making it extremely durable. Often found as rounded pebbles in riverbeds or coastal environments due to water erosion.
Uses & applications
Used in construction as road ballast or crushed stone, in glass manufacturing if high purity, and as decorative landscaping stones or 'worry stones' when tumbled.
Geological facts
Quartzite is one of the most resistant rocks to chemical weathering. This specific specimen has been polished smooth by many years of transport in water, likely a river or ancient glacial deposit.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel knife) and its grainy but fused texture. It is often found as smooth cobbles or pebbles in fluvial (river) deposits worldwide.
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