Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Grayish-white to light gray with translucent patches; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.63–2.65.

Formation & Geological History

Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, the individual quartz grains recrystallize and fuse together into a dense, interlocking mosaic.

Uses & Applications

Used widely in construction as decorative stone, crushed stone for road gravel, and as a source for silica in the manufacturing of glass and ceramics.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges and resistant mountain peaks. It will scratch glass easily.

Field Identification & Locations

Identify in the field by its extreme hardness and the fact that fractures will break through the quartz grains rather than around them (unlike sandstone). Found in folded mountain ranges across the globe.

Identified on: 5/4/2026

Mode: Standard