metamorphic
Light-colored quartz-rich rock, likely quartzite
Quartzite; predominantly crystalline SiO₂, possibly with feldspar or mica impurities
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray-white, granular texture, and vitreous to dull luster. Massive with no obvious cleavage; quartzite typically has specific gravity near 2.65.
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Physical properties
Hardness about 7 Mohs; pale gray-white, granular texture, and vitreous to dull luster. Massive with no obvious cleavage; quartzite typically has specific gravity near 2.65.
Formation & geological history
Formed when quartz-rich sandstone recrystallized under heat and pressure during regional metamorphism. Its exact geological age cannot be determined from the photograph; quartzites range from Precambrian to recent orogenic settings.
Uses & applications
Used as crushed aggregate, road stone, building and paving stone, and occasionally as a decorative material. This irregular specimen has little jewelry value.
Geological facts
Quartzite commonly breaks across quartz grains rather than around them, producing a hard, sharp fracture. The specimen may instead be quartz-rich sandstone or weathered quartz-bearing rock, which cannot be confirmed visually alone.
Field identification & locations
Common in mountain belts and exposed metamorphic terrains worldwide, including the Appalachian and Rocky Mountains. A steel nail should not readily scratch it; acid testing is generally nonreactive unless carbonate minerals are present.
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