Quartzite

Physical Properties

Hardness: 7 (Mohs scale), Color: White, gray, pink, or reddish due to iron oxides, Luster: Vitreous to waxy, Crystal structure: Trigonal/Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7.

Formation & Geological History

Formed from the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together. These rocks can date back to any geological era but are common in Precambrian and Paleozoic shields.

Uses & Applications

Used in construction as crushed stone or decorative facing, in the manufacturing of glass and ceramics, and as a high-silica raw material in metallurgy. Larger, colorful pieces are used as garden stones or lapidary material.

Geological Facts

Quartzite is so tough that it often forms the capstones of hills and mountains because it resists weathering better than surrounding rocks. It is significantly harder than the sandstone it originated from.

Field Identification & Locations

Identify in the field by its hardness (it will easily scratch glass and steel) and its grainy but fused texture; unlike sandstone, it breaks through the quartz grains rather than around them. Common in mountainous regions and riverbeds.

Identified on: 4/22/2026

Mode: Standard