Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: white, gray, or tan with mottled brown; Luster: vitreous to dull; Crystal structure: trigonal (granular texture); Cleavage: none; Specific gravity: 2.63-2.65

Formation & Geological History

Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in orogenic belts. This specific specimen appears to be a water-worn river cobble.

Uses & Applications

Used as crushed stone for road construction, railway ballast, and as a decorative stone in landscaping or as heavy-duty countertops.

Geological Facts

Quartzite is so durable that it often outlasts the mountain ranges from which it originated, frequently appearing as resistant ridges or rounded river stones like the one pictured.

Field Identification & Locations

Identify by its ability to scratch glass and its sugary, granular texture. Commonly found in metamorphic terrains and transported via ancient riverbeds.

Identified on: 4/15/2026

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