Quartzite

Physical Properties

Hardness: 7 (Mohs scale); Color: White, gray, or yellowish/brownish due to iron staining; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 to 2.7

Formation & Geological History

Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. Most quartzite dates from the Precambrian to Paleozoic eras.

Uses & Applications

Used as crushed stone for road construction, railway ballast, and in the manufacturing of glass and ceramics. Polished slabs are used for countertops and flooring.

Geological Facts

Quartzite is often harder and more durable than the parent sandstone. In some cultures, it was used to create stone tools when flint was unavailable because of its sharp conchoidal fracture.

Field Identification & Locations

Can be identified in the field by its inability to be scratched by a steel knife and its sugary, granular texture that looks like fused sand grains. It is commonly found in mountain ranges like the Appalachians or the Alps.

Identified on: 5/10/2026

Mode: Standard