metamorphic

Quartzite

Quartzite (Primary mineral: SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Pinkish-tan/gray; Luster: Vitreous to dull; Crystal Structure: Non-foliated, interlocking quartz grains; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 7 on Mohs scale
Color: Pinkish-tan/gray
Luster: Vitreous to dull

Identified March 16, 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 sand grains to recrystallize and fuse together. The pinkish tint often indicates trace amounts of iron oxide (hematite).

Uses & applications

Commonly used in construction as road ballast, roofing granules, and as a decorative stone in landscaping. High-purity quartzite is used in the glass and metallurgy industries.

Geological facts

Quartzite is so hard that when it breaks, it fractures through the individual sand grains rather than around them, which distinguishes it from sandstone. It is extremely resistant to chemical weathering.

Field identification & locations

Identify in the field by its inability to be scratched by a steel knife and its lack of reaction to acid. Commonly found in folded mountain belts and ancient shield areas like the Appalachians or the Canadian Shield.