Quartzite

Physical Properties

Hardness: 7 (Mohs scale), Color: tan to light brown, Luster: vitreous (glassy) to waxy, Structure: granular and interlocking, Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together, creating an extremely durable rock.

Uses & Applications

Used in construction for road ballast, floor tiles, and countertops. Ground quartzite is also used in glassmaking and as an abrasive.

Geological Facts

Quartzite is one of the most physically durable and chemically resistant rocks found on Earth's surface. When it breaks, it breaks through the quartz grains rather than around them, unlike its parent rock sandstone.

Field Identification & Locations

Identify it by its extreme hardness (it will easily scratch glass) and its crystalline, sugary appearance. It is commonly found in mountain ranges or riverbeds where it has been eroded and rounded into 'river rocks.'

Identified on: 4/13/2026

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