Quartzite

Physical Properties

Hardness: 7 (Mohs), Color: Pinkish-brown or reddish-tan due to iron oxide, Luster: Vitreous to dull, Crystal structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together. Can range from Precambrian to Cenozoic in age.

Uses & Applications

Used as crushed stone for road construction, railway ballast, and in some architectural stones. High-purity quartzite is used to produce glass and metallic silicon.

Geological Facts

Quartzite is so tough that it often survives intense weathering to form the caprock of hills and mountains. It is harder than steel and will easily scratch glass.

Field Identification & Locations

Identify in the field by its sugary texture and hardness; unlike sandstone, quartzite breaks through the quartz grains rather than around them. Found globally in mountainous regions and metamorphic belts.

Identified on: 4/29/2026

Mode: Standard