metamorphic

Rounded gray metamorphic rock, likely quartzite or gneiss

Quartz-rich metamorphic rock; exact identification is uncertain from the photograph

AI-generated identification · may be incorrect

Gray, rounded cobble with pale quartz-rich patches and rusty iron-oxide staining; likely Mohs 6–7, with vitreous to dull luster and weak or absent cleavage. The visible texture may reflect recrystallized quartz and feldspar rather than distinct crystals.

Identified August 9, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when quartz-rich sandstone or felsic rock was subjected to heat and pressure, probably during regional metamorphism; its precise geological age and parent rock cannot be determined visually. The rounded shape indicates later transport by water or glacial action.

Uses & applications

Common specimens have little commercial value, though quartzite is used as aggregate, riprap, paving stone, and dimension stone; attractive pieces may be collected or polished.

Geological facts

A steel file or knife should barely scratch quartzite, while a glass plate can be scratched by fresh quartz-rich surfaces. Rust-colored areas are likely weathered iron-bearing minerals.

Field identification & locations

Common in mountain belts, river gravels, glacial deposits, and exposed metamorphic terrains worldwide; inspect a fresh broken surface and test hardness for better identification. The image also includes a blue-green rock and a small dark fragment, but they are not identifiable confidently.