metamorphic

Quartzite

Quartzite (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Gray, tan, white with yellowish banding; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.7

Hardness: 7 (Mohs scale)
Color: Gray, tan, white with yellowish banding
Luster: Vitreous to waxy

Identified June 18, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize into an interlocking mosaic. Found in orogenic belts worldwide.

Uses & applications

Used as crushed stone for road construction and railway ballast; decorative landscape stone; architectural stone; and occasionally as a gemstone in tumbled form.

Geological facts

Quartzite is so hard that when it breaks, the fracture goes through the individual quartz grains rather than around them, distinguishing it from sandstone. Many river rocks are quartzite due to its extreme resistance to erosion.

Field identification & locations

Identify by its hardness (it will easily scratch glass) and its sugary, crystalline texture under a lens. Commonly found in riverbeds and glacial deposits across North America and Europe.