Quartzite (River Stone)

Physical Properties

Hardness: 7 on Mohs scale; Color: Tan, cream, or off-white; Luster: Vitreous to waxy; Structure: Granular/crystalline; Specific Gravity: 2.6-2.7. It is extremely durable and lacks cleavage.

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. High heat and pressure reciprocal to tectonic compression cause the sand grains to recrystallize and fuse together. Often found as rounded pebbles due to water erosion in riverbeds.

Uses & Applications

Used in construction as crushed stone or ballast, in high-end countertops, and as decorative landscaping stones. Rounded specimens are often used as sensory stones or in beginner rock tumblers.

Geological Facts

Quartzite is so strong that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike sandstone. It is one of the most chemically resistant rocks on Earth.

Field Identification & Locations

Identify in the field by its inability to be scratched by a steel knife and its grainy, sugary look. Commonly found in areas with ancient mountain ranges or in glacial deposits and river basins.

Identified on: 4/22/2026

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