metamorphic

Quartzite

Quartzite (primarily SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Gray, tan, brown, or white; Luster: Vitreous to dull/sugary; Structure: Granular, non-foliated; Cleavage: None (conchoidal fracture); SG: 2.6-2.7

Hardness: 7 (Mohs scale)
Color: Gray, tan, brown, or white
Luster: Vitreous to dull/sugary

Identified July 16, 2026More metamorphic →

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Physical properties

Hardness: 7 (Mohs scale); Color: Gray, tan, brown, or white; Luster: Vitreous to dull/sugary; Structure: Granular, non-foliated; Cleavage: None (conchoidal fracture); SG: 2.6-2.7

Formation & geological history

Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events (orogeny). The original quartz sand grains recrystallize into a dense interlocking mosaic.

Uses & applications

Used in construction as crushed stone or building stone, in glass manufacturing if highly pure, and as decorative stone in landscaping or interior design.

Geological facts

Quartzite is so hard and chemically resistant that it often forms the caps of ridges and mountains. It is harder than steel and will easily scratch glass.

Field identification & locations

Identify by its hardness (scratches glass) and its granular, crystalline appearance that sparkles slightly in light. Found worldwide in ancient mountain belts like the Appalachians or Alps.