Quartzite

Physical Properties

Hardness: 7 on Mohs scale (will scratch glass); Color: Brownish-pink to tan; Luster: Vitreous to dull/waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.

Formation & Geological History

Formed through the regional or contact metamorphism of quartzose sandstone. Under high heat and pressure, the individual quartz grains recrystallize and fuse together into a dense, crystalline rock. The brownish/pink color is often due to trace amounts of iron oxides.

Uses & Applications

Used in construction as road ballast, gravel, and dimension stone for flooring or wall coverings. Highly durable for landscaping and sometimes used in glassmaking if pure enough.

Geological Facts

Quartzite is so tough that it often survives intense weathering and erosion that destroys surrounding rocks, frequently forming the tops of ridges and mountains. It is harder than the sandstone it originates from.

Field Identification & Locations

Identify in the field by its hardness (it should easily scratch a steel knife or glass) and its sugary texture. Unlike sandstone, which breaks around grains, quartzite breaks through the grains. Found worldwide in mountain belts and shield areas.

Identified on: 4/15/2026

Mode: Standard