metamorphic

Quartzite (probable)

Quartz-rich metamorphic rock, composed mainly of SiO₂ quartz

AI-generated identification · may be incorrect

Typically Mohs hardness 7, pale gray to tan with rusty iron-oxide staining, and a vitreous to dull weathered luster. Its granular quartz mosaic is massive, with no obvious cleavage; individual grains commonly fracture rather than split.

Identified September 15, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when quartz-rich sandstone is recrystallized under heat and pressure during regional metamorphism. The specimen’s exact geological age cannot be determined from an image; quartzite occurs in Precambrian through younger metamorphic terrains.

Uses & applications

Used as durable aggregate, road stone, building and decorative stone, and occasionally as a lapidary material. This ordinary rounded specimen has little commercial value.

Geological facts

Quartzite is commonly harder and more resistant to weathering than its parent sandstone, so it often survives as stream cobbles and ridge-forming outcrops.

Field identification & locations

Identify it by testing whether it scratches glass and by looking for fused quartz grains that break across grain boundaries; sandstone usually shows weaker grain cohesion. Common in metamorphic mountain belts worldwide, including the Appalachians, Rockies, Scandinavia, India, and Brazil.