metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly quartz (SiO₂), with minor feldspar, mica, and iron-oxide staining
AI-generated identification · may be incorrectTypically Mohs hardness 7, granular and very resistant; this specimen is cream to tan with dark gray-brown mineral patches, vitreous to dull luster, and interlocking quartz grains lacking cleavage. The rounded surface appears naturally weathered or possibly tumbled.
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Physical properties
Typically Mohs hardness 7, granular and very resistant; this specimen is cream to tan with dark gray-brown mineral patches, vitreous to dull luster, and interlocking quartz grains lacking cleavage. The rounded surface appears naturally weathered or possibly tumbled.
Formation & geological history
Formed when quartz-rich sandstone recrystallized under elevated temperature and pressure, generally during regional metamorphism; its exact geological age cannot be determined from the image. Dark areas may represent mica, amphibole, biotite, or iron/manganese oxides.
Uses & applications
Used as crushed stone, aggregate, paving, building stone, and decorative material; attractive pieces may be collected or polished, though this specimen has limited gem value.
Geological facts
Quartzite commonly breaks across grains rather than around them, making fresh surfaces sparkly and resistant to scratching. It can resemble marble, but quartzite is harder and does not fizz with dilute hydrochloric acid.
Field identification & locations
Common in metamorphic mountain belts worldwide, including the Appalachians, Rocky Mountains, Alps, and India. Test with a steel file or glass (quartzite should scratch glass), inspect for sugary quartz texture, and avoid relying on color alone.
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