metamorphic
Quartzite Pebble
Metamorphic Quartzite
Hardness: 7 on Mohs scale. Color: Generally white, gray, yellowish, or brownish due to iron oxide impurities. Luster: Vitreous to greasy on fresh surfaces. Crystal structure: Interlocking quartz crystals, massive. Cleavage: None, breaks with a conchoidal fracture. Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to greasy on fresh surfaces
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Physical properties
Hardness: 7 on Mohs scale. Color: Generally white, gray, yellowish, or brownish due to iron oxide impurities. Luster: Vitreous to greasy on fresh surfaces. Crystal structure: Interlocking quartz crystals, massive. Cleavage: None, breaks with a conchoidal fracture. Specific gravity: 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert that has been subjected to intense heat and pressure (regional or contact metamorphism). During this metamorphic process, the original quartz grains recrystallize along with the cementing material, interlocking them tightly.
Uses & applications
Used in construction, as crushed stone for roadbeds, railway ballast, manufacturing silica bricks, and occasionally as an ornamental stone or in landscaping.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich rocks often survive as pebbles and boulders in riverbeds long after softer rocks have eroded away.
Field identification & locations
Can be identified in the field by its hardness (it will easily scratch glass and cannot be scratched by a steel knife) and the fact that it breaks across the quartz grains rather than around them, unlike sandstone. Found globally in ancient mountain belts and river gravels.
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