metamorphic

Quartz-rich metamorphic rock, possibly quartzite

Quartzite; primarily crystalline silicon dioxide (SiO₂), with minor feldspar, mica, or iron oxides

AI-generated identification · may be incorrect

Hardness about 7 Mohs; gray to whitish with rusty brown staining, granular texture, and glassy to dull luster. Quartzite lacks strong cleavage and commonly breaks irregularly or conchoidally; exact identification is limited by the photograph.

Identified August 8, 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, commonly during mountain-building events. Its age depends on the source sandstone and metamorphic event, ranging from Precambrian to younger rocks.

Uses & applications

Used as crushed stone, aggregate, riprap, paving, and occasionally decorative building stone; attractive specimens may be collected but this example appears common-grade.

Geological facts

Quartzite is generally harder and more resistant to weathering than its sandstone precursor. Iron-oxide staining produces the reddish-brown patches visible here.

Field identification & locations

Likely quartzite if the gray grains are tightly fused and the rock scratches glass; sandstone if grains are visibly loose or gritty. Common in metamorphic mountain belts worldwide, including the Appalachians, Rocky Mountains, and Precambrian shields.