Quartzite

Physical Properties

Hardness: 7 on Mohs scale. Color: typically white to gray, often showing pink, red, or yellow tints from iron oxides. Luster: Vitreous to dull. Structure: Granoblastic, non-foliated. Cleavage: None (conchoidal fracture).

Formation & Geological History

Forms when quartz-rich sandstone is subjected to high heat and pressure during regional metamorphism. The quartz grains recrystallize and fuse into an interlocking mosaic of crystals.

Uses & Applications

Used as a decorative stone in construction, railway ballast, road aggregate, and as a source of silica for glass and abrasive manufacturing.

Geological Facts

Quartzite is so tough that it often outlasts other surrounding rocks during erosion, frequently forming the peaks of mountains and ridges. It is harder than steel and can easily scratch glass.

Field Identification & Locations

Identify in the field by its extreme hardness and the fact that it breaks across the quartz grains rather than around them (unlike sandstone). Commonly found in mountain belts worldwide.

Identified on: 5/6/2026

Mode: Standard