metamorphic

Red-brown quartzite or quartz-rich sandstone

Quartzite; predominantly microcrystalline quartz (SiO₂), possibly with iron-oxide impurities

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; pinkish red-brown, dull to subtly glassy luster, massive and fine-grained, with no obvious cleavage. The rounded surface and conchoidal-looking chips suggest a silica-rich rock, though the image cannot distinguish quartzite confidently from weathered sandstone.

Identified September 11, 2026More metamorphic →

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Physical properties

Formation & geological history

Quartzite forms when quartz-rich sandstone is metamorphosed and recrystallized under heat and pressure, commonly during mountain building; its age depends on the original sandstone and metamorphic event. Iron oxides produce the reddish coloration.

Uses & applications

Used as crushed aggregate, road stone, building and paving stone, and occasionally as decorative stone; attractive pieces are collected but are generally not gem material.

Geological facts

Quartzite is typically harder and more resistant to weathering than sandstone, often breaking across quartz grains rather than around them. Red coloration commonly comes from hematite or limonite coatings and cement.

Field identification & locations

Test with a steel nail or glass: quartzite generally scratches glass and resists a steel knife. Common worldwide in metamorphic belts, including the Appalachians, Rocky Mountains, and Scandinavian mountains; a geological setting or fresh fracture is needed for certainty.