Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Gray, white, or yellowish; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None; Specific gravity: 2.6-2.7

Formation & Geological History

Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the original quartz grains to recrystallize into an interlocking mosaic.

Uses & Applications

Used as building stone, decorative paving, crushed stone for road construction, and occasionally in glass manufacturing if pure enough.

Geological Facts

Quartzite as a rock is so tough that it often breaks through the quartz grains rather than along their boundaries, unlike the sandstone it originated from.

Field Identification & Locations

Identify by its extreme hardness (it will scratch glass and steel) and its grainy but fused appearance. Commonly found in folded mountain belts and ancient shield areas.

Identified on: 5/1/2026

Mode: Standard