Quartzite

Physical Properties

Hardness: 7 (Mohs scale); Color: White, grey, or tan; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together, creating an extremely durable rock. Primarily found in mountain belts and Precambrian shields.

Uses & Applications

Used as crushed stone for road construction and railway ballast; used in architecture as decorative wall coverings, flooring, and kitchen countertops; high-purity quartzite is used to produce ferrosilicon and industrial silica.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rock, forming prominent ridges and peaks. It is often confused with marble, but can be distinguished because quartzite will scratch glass while marble will not.

Field Identification & Locations

Identify in the field by its grainy, sandpaper-like texture (inherited from sandstone) but with a crystalline shimmer. It will not react with acid. Commonly found in areas with ancient mountain ranges or riverbeds following erosion of mountains.

Identified on: 4/15/2026

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