Quartzite

Physical Properties

Hardness: 7 (Mohs scale); Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal crystals within a granoblastic texture; Cleavage: None; Specific gravity: 2.6 - 2.7.

Formation & Geological History

Formed through the metamorphism of quartz sandstone under high heat and pressure, causing the original quartz grains to recrystallize and fuse together. Often found in orogenic (mountain-building) belts.

Uses & Applications

Used in construction as road ballast, decorative stone, flooring, and wall coverings. Due to its hardness, it is also used as an abrasive and in the manufacturing of glass and ceramics.

Geological Facts

Quartzite is so hard and chemically resistant that it often forms the tops of ridges and mountains because it resists weathering better than the surrounding rock types. It is often confused with marble but will easily scratch glass, whereas marble will not.

Field Identification & Locations

Identify by its ability to scratch glass and its sugary, crystalline surface texture. Unlike sandstone, when quartzite breaks, the fracture passes through the quartz grains rather than around them. Found globally in old metamorphic terrains.

Identified on: 4/25/2026

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