Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white, gray, or translucent, sometimes with greenish or reddish tints; Luster: vitreous (glassy) to waxy; Texture: granular, crystalline; Cleavage: none, breaks with a conchoidal or irregular fracture.

Formation & Geological History

Quartzite forms from the metamorphism of quartz-rich sandstone. High heat and pressure cause the original quartz grains to recrystallize and fuse into a solid, interlocking network. It is found in mountain belts globally where sedimentary basins have been compressed.

Uses & Applications

Used as crushed stone for road construction, railway ballast, and building stone. High-purity quartzite is used in the manufacture of glass, silicon metal, and ferrosilicon. It is also a popular material for countertops and decorative stone.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rocks during erosion, often forming the caps of hills or ridges. It is frequently mistaken for marble, but can be distinguished because quartzite will scratch glass and marble will not.

Field Identification & Locations

Identify in the field by its extreme hardness, sugar-like granular appearance on fresh surfaces, and the fact that it breaks across the grains rather than around them. Common in old metamorphic shields and folded mountain ranges.

Identified on: 5/11/2026

Mode: Standard