Quartzite

Physical Properties

Hardness: 7 (Mohs scale); Color: White, gray, or buff; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.7

Formation & Geological History

Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together, creating a dense, interlocking matrix. It is found in ancient mountain belts and mobile zones worldwide.

Uses & Applications

Used as a decorative stone in construction (countertops, wall cladding), as railway ballast, in road gravel, and occasionally as a source of silica for glass manufacturing.

Geological Facts

Quartzite is so hard that it will scratch steel. It is more resistant to weathering than the sandstone it originated from, often forming the peaks of resistant mountain ridges.

Field Identification & Locations

Identify in the field by its sugary texture and extreme hardness (it will easily scratch a knife blade or glass). Look for it in areas with high-grade metamorphic activity. Collectors value pieces with unique crystallization or desert varnish.

Identified on: 4/19/2026

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