metamorphic

Quartzite

Quartzite (primarily SiO2)

AI-generated identification · may be incorrect

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

Hardness: 7 on Mohs scale
Color: Gray, white, or yellowish
Luster: Vitreous to dull

Identified April 24, 2026More metamorphic →

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Physical properties

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

Formation & geological history

Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny). The individual quartz grains recrystallize into a locked mosaic.

Uses & applications

Used as crushed stone for road construction, railway ballast, and as a raw material in the glass and silicate industries. Polished slabs are used for countertops and flooring.

Geological facts

Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges and peaks. It is frequently mistaken for marble but can be distinguished by its superior hardness.

Field identification & locations

Identify in the field by its inability to be scratched by a steel knife and its sugary, granular texture on fresh surfaces. It is found globally in folded mountain belts and ancient shield areas.