metamorphic

Gray quartzite or quartz-rich metamorphic rock

Quartzite; predominantly crystalline SiO₂, possibly with minor feldspar, mica, or iron oxides

AI-generated identification · may be incorrect

Hardness about 7 Mohs; gray to beige, massive and granular, with a dull to slightly vitreous luster. It lacks obvious cleavage and commonly shows interlocking quartz grains, though the image alone cannot confirm the diagnosis.

Identified September 11, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when quartz-rich sandstone was recrystallized under heat and pressure during regional metamorphism; ages vary widely depending on the source formation. Common in Precambrian and mountain-belt terrains.

Uses & applications

Used as building stone, landscaping aggregate, road material, countertops, and occasionally as a decorative or lapidary specimen.

Geological facts

Quartzite is typically harder and more resistant to weathering than its sandstone precursor. A fresh break commonly cuts through quartz grains rather than around them.

Field identification & locations

Common in metamorphic mountain belts worldwide, including the Appalachians, Rocky Mountains, Alps, and Precambrian shields. Test with a steel nail or glass: genuine quartzite should scratch glass and resist a steel blade; acid produces no reaction.