Quartzite River Rock

Physical Properties

Hardness: 7 on Mohs scale; Color: Tan to light brown with fine-grained texture; Luster: Dull to slightly waxy; Crystal Structure: Non-foliated, interlocking quartz grains; Specific Gravity: 2.6-2.7.

Formation & Geological History

Formed through the metamorphism of quartz sandstone under intense heat and pressure. These specific rounded shapes are produced by fluvial (river) erosion over thousands of years.

Uses & Applications

Used in landscaping, construction aggregate, and as decorative garden stones. High-purity quartzite can be used to produce silica sand for glassmaking.

Geological Facts

Quartzite is so hard that it will scratch glass and steel. It is more resistant to weathering than the sandstone it originated from, which is why it often survives as rounded pebbles in riverbeds.

Field Identification & Locations

Identify in the field by its hardness (cannot be scratched by a knife) and its grainy, sandpaper-like texture that has been smoothed over. Commonly found in riverbeds, glacial deposits, and beaches.

Identified on: 4/13/2026

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