metamorphic

Weathered quartz-rich rock, likely quartzite

Quartzite; predominantly crystalline SiO₂

AI-generated identification · may be incorrect

Hardness about 7 Mohs; gray-beige, massive, and unevenly granular with a dull to sugary vitreous luster. Quartzite has interlocking quartz crystals, no obvious cleavage, and specific gravity near 2.65; the pictured specimen is heavily weathered and possibly iron-stained.

Identified September 10, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when quartz-rich sandstone is recrystallized under heat and pressure during metamorphism, commonly during mountain building. Its exact geological age cannot be determined from the photograph and may range from Precambrian to recent tectonic belts.

Uses & applications

Used as crushed stone, aggregate, road material, dimension stone, and occasionally countertops or decorative specimens. This rough, weathered piece has little jewelry value.

Geological facts

Quartzite is generally more resistant to weathering than the sandstone from which it forms, often producing ridges and resistant boulders.

Field identification & locations

Field identification relies on its very high hardness: it scratches glass and commonly breaks across grains rather than around them; unlike marble, it does not fizz readily with dilute acid. Common worldwide in metamorphic mountain regions.