Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Reddish-brown, pink, tan, or gray; Luster: Dull to vitreous; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, original quartz grains recrystallize and fuse into an interlocking mosaic of crystals. Age varies by location but occurs throughout geological history.

Uses & Applications

Used as crushed stone for road construction, railway ballast, and as a raw material in the glass and silicate industries. Polished samples are used for countertops, floor tiles, and decorative landscaping stones.

Geological Facts

Quartzite is so durable that it often outlasts the surrounding rocks during erosion, frequently forming the tops of ridges and hills. It is often confused with marble but can be distinguished because quartzite will not fizz in contact with acid.

Field Identification & Locations

Identify in the field by its extreme hardness (it will scratch glass and steel) and its granular, sugary texture. It is commonly found in mountain ranges and glacial deposits as rounded cobbles.

Identified on: 5/3/2026

Mode: Standard