metamorphic

Quartz-rich metamorphic rock, likely quartzite

Quartzite; predominantly microcrystalline quartz (SiO₂), possibly with mica or feldspar

AI-generated identification · may be incorrect

Typically very hard (Mohs 7), gray-white, granular, and vitreous to dull; quartz grains are tightly interlocked with little visible cleavage. The specimen appears weathered and rounded, though its exact identity is uncertain from the photograph.

Identified September 3, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when quartz-rich sandstone is recrystallized under heat and pressure during regional or contact metamorphism, commonly during mountain building. Its age depends on the source formation and may range from Precambrian to younger Phanerozoic.

Uses & applications

Used as crushed stone, aggregate, dimension stone, countertops, roofing material, and decorative landscaping rock; attractive pieces may be collected but are generally low value.

Geological facts

Quartzite is commonly confused with quartz-rich sandstone; unlike sandstone, it tends to fracture through quartz grains rather than around them. A steel nail usually will not scratch it.

Field identification & locations

Common in metamorphic belts worldwide, including the Appalachian, Rocky, and Himalayan regions. Confirm with a hardness test, acid test for carbonate minerals, and inspection for fused quartz grains; the nearby rounded pebble may be a different quartz-rich rock.