metamorphic

Quartzite

Quartzite (chiefly SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: typically white to gray, often with pink/yellow/brown hues due to iron minerals; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 7 on Mohs scale
Luster: Vitreous to dull

Identified May 24, 2026More metamorphic →

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Physical properties

Formation & geological history

Quartzite is formed through the metamorphism of quartz sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, resulting in a very hard and durable rock. It forms in mountain-building tectonic environments.

Uses & applications

Used as crushed stone in road construction and railway ballast; as dimension stone for flooring, wall coverings, and countertops; and as a source of silica for glass manufacturing.

Geological facts

Quartzite is so tough that it often outlasts the mountains it forms. In a thin section analysis, the original boundaries of the sand grains disappear as they weld into a solid mass of interlocking quartz crystals.

Field identification & locations

Identification in the field: It will scratch glass easily and will not react with acid (unlike marble). Look for a sugary, granular texture that breaks across the grains rather than around them. Found globally in ancient shield regions and mountain belts.