metamorphic
Quartzite Pebble
Quartzite (mostly SiO2)
Hardness: 7 on Mohs scale; Color: reddish-brown with white mottling; Luster: dull to vitreous; Structure: granular/crystalline; Cleavage: none; Specific gravity: approx. 2.65.
- Hardness
- 7 on Mohs scale
- Color
- reddish-brown with white mottling
- Luster
- dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: reddish-brown with white mottling; Luster: dull to vitreous; Structure: granular/crystalline; Cleavage: none; Specific gravity: approx. 2.65.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, often during mountain-building events. This specific specimen has been rounded by fluvial or glacial transport.
Uses & applications
Commonly used as decorative gravel, in landscaping, and as a durable construction aggregate. Small pebbles are popular for rock tumbling.
Geological facts
Quartzite is so tough that it often survives multiple cycles of erosion and deposition. It is typically harder and more resistant than the sandstone from which it originated.
Field identification & locations
Identify in the field by its extreme hardness (it will scratch glass) and its grainy, sugary texture. It is ubiquitous in riverbeds and glacial tills worldwide.
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