Quartzite River Rock

Physical Properties

Hardness: 7 on Mohs scale; Color: Brownish-tan surface with possible white/gray interior; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: Indistinct/none; Specific gravity: 2.6-2.7

Formation & Geological History

Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. This specimen is a cobble smoothed by river or glacial transport.

Uses & Applications

Used primarily in construction as crushed stone or road ballast, as a decorative landscape stone, and sometimes for high-silica industrial applications.

Geological Facts

Quartzite is so durable that it often outlasts the mountains it was part of, appearing as resistant river boulders long after softer rocks have eroded away.

Field Identification & Locations

Identify by its extreme hardness (cannot be scratched by steel) and lack of visible grains compared to sandstone. Commonly found in riverbeds, glacial tills, and ancient metamorphic belts.

Identified on: 5/2/2026

Mode: Standard