metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly microcrystalline quartz (SiO₂), possibly with mica or iron-oxide impurities
AI-generated identification · may be incorrectHardness about 7 Mohs; gray to dark brown, with sparkly vitreous quartz grains and uneven fracture. Quartzite is nonfoliated and lacks obvious cleavage; its dense texture and specific gravity are typically about 2.6–2.7.
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Physical properties
Hardness about 7 Mohs; gray to dark brown, with sparkly vitreous quartz grains and uneven fracture. Quartzite is nonfoliated and lacks obvious cleavage; its dense texture and specific gravity are typically about 2.6–2.7.
Formation & geological history
Formed when quartz-rich sandstone recrystallized under heat and pressure, commonly during regional mountain-building; the specimen’s exact geological age cannot be determined from the image. Dark coloration may reflect biotite, graphite, or iron oxides.
Uses & applications
Used as crushed stone, aggregate, road material, building stone, and decorative slabs; attractive pieces may be collected, but this rough specimen has limited gem value.
Geological facts
Quartzite commonly preserves a sugary, interlocking quartz texture, unlike sandstone, whose individual grains can often be rubbed loose. A steel file generally fails to scratch fresh quartzite.
Field identification & locations
Likely quartzite based on its massive, glittering quartz-rich appearance, but schist or quartz-veined metamorphic rock is also possible. Common in metamorphic belts worldwide; test a fresh surface with a steel file and inspect for mica layering.
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