metamorphic

Iron-stained quartzite

Quartzite, predominantly SiO₂, with hematite/goethite staining

AI-generated identification · may be incorrect

Typically 7 Mohs, very hard and resistant; white to gray quartz with reddish-brown iron-oxide patches, vitreous to sugary luster, interlocking granular crystals, and no obvious cleavage. The specimen appears massive, weathered, and partly brecciated or strongly stained.

Identified September 6, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when quartz-rich sandstone was metamorphosed under heat and pressure, recrystallizing the quartz grains; iron-bearing fluids later produced hematite/goethite coloration. Its exact geological age cannot be determined from the photograph; quartzites range from Precambrian to recent mountain belts.

Uses & applications

Used as crushed stone, aggregate, road material, building stone, and decorative landscaping rock; attractive pieces are collected or polished, though this example appears chiefly a field specimen.

Geological facts

Quartzite commonly breaks across grains rather than around them and can scratch glass. Red coloration generally indicates oxidized iron rather than ruby or garnet.

Field identification & locations

Identify by its exceptional hardness, quartz-rich texture, and resistance to dilute acid; unlike sandstone, grains are fused and the surface feels sugary or glassy. Common in metamorphic mountain belts worldwide, including the Appalachians, Rocky Mountains, and Precambrian shields.