metamorphic
Iron-stained quartzite or quartz-rich rock
Quartzite, predominantly crystalline SiO₂, with iron-oxide minerals such as hematite and goethite
AI-generated identification · may be incorrectHardness about 7 Mohs; brown, rusty orange, gray, and translucent patches; glassy to dull luster; interlocking quartz grains with no obvious cleavage, commonly showing conchoidal fracture. The specimen appears strongly weathered and iron-stained.
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Physical properties
Hardness about 7 Mohs; brown, rusty orange, gray, and translucent patches; glassy to dull luster; interlocking quartz grains with no obvious cleavage, commonly showing conchoidal fracture. The specimen appears strongly weathered and iron-stained.
Formation & geological history
Formed when quartz-rich sandstone recrystallized under heat and pressure, generally during regional metamorphism; its exact geological age cannot be determined from the photograph. Iron-bearing fluids or weathering produced the brown-red coatings.
Uses & applications
Used as crushed stone, aggregate, paving, building stone, and decorative rock; attractive pieces may be collected but are usually low-value unless unusually crystalline or scenic.
Geological facts
Quartzite commonly resists weathering better than surrounding rocks, forming ridges and durable boulders. Iron oxides can mimic metallic mineralization but are typically earthy rather than truly metallic.
Field identification & locations
Look for quartz-like hardness— it scratches ordinary glass—and a sugary, fused texture rather than loose sandstone grains; a streak test may show little or reddish-brown powder. Common in metamorphic belts worldwide, including the Appalachians, Rocky Mountains, and Precambrian shields.
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