metamorphic
Quartzite pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: tan, light brown, or off-white; Luster: dull to vitreous; Structure: non-foliated, granular; Cleavage: none; Specific Gravity: 2.62.65.
- Hardness
- 7 on Mohs scale
- Color
- tan, light brown, or off-white
- Luster
- dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, light brown, or off-white; Luster: dull to vitreous; Structure: non-foliated, granular; Cleavage: none; Specific Gravity: 2.62.65.
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure, causing sand grains to recrystallize and fuse together. The rounded shape indicates high-energy water transport (river or beach erosion).
Uses & applications
Used as aggregate in construction, road ballast, industrial silica source for glass making, and decorative landscaping stone.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than around them, unlike sandstone. It is often harder than the steel of a pocket knife.
Field identification & locations
Identify by its ability to scratch glass and its sugary, granular texture that looks like fused sand. Found in riverbeds, glacial deposits, or ancient metamorphic belts worldwide.
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