metamorphic
Weathered quartz-rich rock, likely quartzite
Quartzite; predominantly quartz (SiO₂), possibly with feldspar and iron-oxide staining
AI-generated identification · may be incorrectTypically Mohs hardness ~7, pale gray to tan, with a vitreous to sugary luster and interlocking quartz grains; massive, with no obvious cleavage. The specimen appears strongly weathered and may contain mica or feldspar, so a field photo alone cannot confirm the identification.
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Physical properties
Typically Mohs hardness ~7, pale gray to tan, with a vitreous to sugary luster and interlocking quartz grains; massive, with no obvious cleavage. The specimen appears strongly weathered and may contain mica or feldspar, so a field photo alone cannot confirm the identification.
Formation & geological history
Quartzite forms when quartz-rich sandstone is recrystallized during regional metamorphism, commonly during mountain building. Its exact geological age depends on the source sandstone and metamorphic event.
Uses & applications
Crushed quartzite is used for aggregate, roadstone, and construction; high-purity material is used for silica products. Attractive pieces have modest value as educational or lapidary specimens.
Geological facts
Quartzite is generally harder and more resistant to weathering than the sandstone from which it formed. Iron oxides commonly produce the tan, orange, or rusty coloration visible here.
Field identification & locations
Look for grains fused into a hard, sugary mass; broken surfaces should cut through grains rather than separate along bedding. A steel file should not scratch fresh quartz-rich areas, while vinegar should produce no reaction; common sources include metamorphic mountain belts worldwide.
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