Quartzite

Physical Properties

Hardness: 7 (Mohs scale), Color: White to pale purple/lavender due to impurities, Luster: Vitreous to sugary, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None (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 sand grains to recrystallize and fuse into a solid mass. Most found today are Precambrian to Paleozoic in age.

Uses & Applications

Used in construction for road ballast and railway tracks, as a dimension stone for flooring and countertops, and in industrial glass making due to high silica content. Small colorful pieces are often sold in rock kits for kids.

Geological Facts

Quartzite is so strong that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike its parent stone, sandstone.

Field Identification & Locations

Identify in the field by its superior hardness (it will easily scratch glass) and its sugary, crystalline texture that sparkles under light. Found globally in mountainous regions where tectonic activity has occurred.

Identified on: 5/18/2026

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