Quartzite

Physical Properties

Hardness: 7 (Mohs scale); Color: White, gray, or tan (often yellowish/brown from iron oxide staining); Luster: Vitreous to greasy; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.

Formation & Geological History

Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the individual quartz grains to recrystallize and fuse together into a dense, interlocking mosaic.

Uses & Applications

Used as a decorative stone in construction, road ballast, manufacture of glass and ceramics, and as a durable material for countertops and flooring.

Geological Facts

Quartzite is so tough that it often survives intense erosion to form the crests of mountain ridges. Unlike sandstone, when quartzite is broken, it fractures through the quartz grains rather than around them.

Field Identification & Locations

Identify in the field by its extreme hardness (cannot be scratched by a steel nail) and its granular, sugary texture. Found globally in mountainous regions and areas of intense tectonic activity.

Identified on: 4/29/2026

Mode: Standard