Quartzite

Physical Properties

Hardness: 7 (Mohs scale), Color: White to yellowish-tan, Luster: Vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: Indistinct/Conchoidal fracture, Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together into a dense, hard rock. It is found in mountain belts and metamorphic terrains globally.

Uses & Applications

Used in construction as crushed stone for road gravel and rail ballast, as dimension stone for flooring and wall coverings, and occasionally in glassmaking if the silica content is very high.

Geological Facts

Quartzite is so hard that it will scratch glass and steel. Unlike sandstone, which breaks between grains, quartzite breaks through the grains due to the complete recrystallization of the silica.

Field Identification & Locations

Identify by its extreme hardness and sugary, crystalline texture on a fresh break. It is often found in hilly landscapes because it is highly resistant to chemical and physical weathering.

Identified on: 4/30/2026

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