metamorphic
Quartzite River Rock
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: tan, grey, or white with a sugary texture; Luster: dull to vitreous; Crystal structure: Non-foliated granoblastic; Cleavage: none; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- tan, grey, or white with a sugary texture
- Luster
- dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, grey, or white with a sugary texture; Luster: dull to vitreous; Crystal structure: Non-foliated granoblastic; Cleavage: none; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, often reshaped into rounded cobbles by fluvial (river) or glacial transport processes.
Uses & applications
Used in construction as crushed stone, railway ballast, and decorative landscaping rock. Exceptionally durable for outdoor use.
Geological facts
Quartzite is so hard that it will scratch glass and even spark when struck against steel. It is more resistant to weathering than the sandstone from which it originated.
Field identification & locations
Identify by its hardness (cannot be scratched by a steel nail) and the way it breaks through quartz grains rather than around them. Commonly found in riverbeds and glacial deposits.
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