metamorphic
Quartzite Pebble
Metamorphic Rock consisting of Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white to tan with slight translucency; Luster: Vitreous to waxy; Texture: Granoblastic, sugary texture under close inspection; Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white to tan with slight translucency
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white to tan with slight translucency; Luster: Vitreous to waxy; Texture: Granoblastic, sugary texture under close inspection; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under high heat and pressure, original quartz grains recrystallize and fuse together into a dense, hard rock. This specimen has been rounded by fluvial (river) or glacial transport.
Uses & applications
Quartzite is used heavily in the construction industry as crushed stone for road beds or railroad ballast. Water-worn pebbles are popular for decorative landscaping, aquariums, and rock tumbling for hobbyists.
Geological facts
Quartzite is so durable that it often survives intense weathering and erosion better than the rocks surrounding it, frequently forming the tops of ridges and mountains. It is harder than a steel knife and will easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness and its sugary, crystalline surface which differentiates it from the 'dull' look of sandstone. Found globally in riverbeds and glacial tills. Collectors look for translucent or uniquely colored varieties.
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