metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite (mostly microcrystalline quartz, SiO₂), possibly mica-bearing
AI-generated identification · may be incorrectHardness about 7 Mohs; irregular, massive texture with gray, white, tan, and dark patches, vitreous to dull luster, and no obvious cleavage. The dark areas may be mica or iron/manganese-stained minerals; exact identification requires testing.
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Physical properties
Hardness about 7 Mohs; irregular, massive texture with gray, white, tan, and dark patches, vitreous to dull luster, and no obvious cleavage. The dark areas may be mica or iron/manganese-stained minerals; exact identification requires testing.
Formation & geological history
Formed when quartz-rich sandstone recrystallized under heat and pressure during metamorphism; its age depends on the original sandstone and regional tectonic event. Common in mountain belts and exposed metamorphic terrains.
Uses & applications
Used as crushed stone, aggregate, building stone, countertops, and decorative specimens; attractive pieces may be collectible but are generally low value.
Geological facts
Quartzite commonly breaks across quartz grains rather than around them, producing a rough, sugary fracture. The specimen’s irregular dark inclusions could also indicate a different metamorphic rock, such as mica-rich schist or gneiss.
Field identification & locations
Test for glass-scratching hardness and lack of reaction to dilute acid; quartzite typically does not fizz. Common sources include the Appalachians, Rocky Mountains, Brazil, India, and Scandinavia; verify with a streak, hardness, and close-grained examination.
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