metamorphic

Quartzite River Rock

Quartzite (primarily SiO2)

AI-generated identification · may be incorrect

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

Identified May 9, 2026More metamorphic →

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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.