metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite (mostly crystalline SiO₂), possibly quartz-rich schist or vein quartz
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray, tan, and brown with a glassy to pearly luster and irregular fracture. The specimen appears massive and coarse-grained, though the image is insufficient to confirm foliation or individual crystals.
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Physical properties
Hardness about 7 Mohs; pale gray, tan, and brown with a glassy to pearly luster and irregular fracture. The specimen appears massive and coarse-grained, though the image is insufficient to confirm foliation or individual crystals.
Formation & geological history
Forms when quartz sandstone is recrystallized under heat and pressure during regional metamorphism; commonly Precambrian to younger, depending on its geologic setting.
Uses & applications
Used as crushed stone, aggregate, building stone, and decorative material; attractive pieces are collected, but this irregular specimen has modest commercial value.
Geological facts
Quartzite resists weathering and commonly forms prominent ridges. Unlike marble, it does not fizz with dilute hydrochloric acid unless carbonate minerals are present.
Field identification & locations
Look for quartz grains fused into a hard, non-friable mass; it should scratch ordinary glass and resist a steel knife. Common worldwide in metamorphic belts, including the Appalachians, Rocky Mountains, India, Brazil, and Scandinavia.
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