Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Tan, beige, or yellowish-brown due to iron impurities; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None, breaks with conchoidal fracture; Specific gravity: 2.6-2.7.

Formation & Geological History

Formed from the metamorphism of quartz sandstone under intense heat and pressure. This process causes quartz grains to recrystallize and fuse together, creating an extremely durable rock. Common in convergent plate boundaries.

Uses & Applications

Used as a crushed stone in construction, road ballast, and as a decorative stone in landscaping. High-purity quartzite is used to produce silica for glassmaking and silicon industrial products.

Geological Facts

Quartzite is so hard that it will scratch glass and steel. In prehistoric times, it was occasionally used as a source for stone tools, though it is more difficult to flake than flint or chert.

Field Identification & Locations

Identified in the field by its hardness and granular, sugary appearance. Unlike sandstone, quartzite breaks through the sand grains rather than around them. Found globally in mountainous regions and ancient continental shields.

Identified on: 5/3/2026

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