Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white to grey, but can be pink or reddish; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the metamorphism of quartz sandstone under high heat and pressure, causing quartz grains to recrystallize and fuse together.

Uses & Applications

Used as a decorative stone in architecture, as railway ballast, in road construction, and occasionally for high-end countertops or as a source of silica for glass manufacturing.

Geological Facts

Quartzite is so tough that it usually breaks through the quartz grains rather than along their boundaries, unlike the sandstone from which it originated.

Field Identification & Locations

Identify in the field by its extreme hardness (cannot be scratched by steel) and its grainy, sugary texture with a lack of layering compared to schist. Commonly found in folded mountain belts globally.

Identified on: 5/1/2026

Mode: Standard