metamorphic
Weathered quartzite cobble
Quartzite, predominantly crystalline SiO₂
AI-generated identification · may be incorrectTypically Mohs hardness 7, white to gray or tan, and vitreous to dull/waxy where weathered; quartz grains are tightly interlocked, with no obvious cleavage and high resistance to scratching. The specimen shows pale quartz-rich banding or veining and rounded stream-weathering.
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Physical properties
Typically Mohs hardness 7, white to gray or tan, and vitreous to dull/waxy where weathered; quartz grains are tightly interlocked, with no obvious cleavage and high resistance to scratching. The specimen shows pale quartz-rich banding or veining and rounded stream-weathering.
Formation & geological history
Formed when quartz-rich sandstone was recrystallized during regional metamorphism, commonly during mountain-building events; its exact geological age cannot be determined from the image. Resistant fragments accumulate in streambeds, talus, and glacial deposits.
Uses & applications
Used as crushed stone, aggregate, road material, dimension stone, countertops, and decorative landscaping rock; attractive pieces may be collected or polished. It is generally not a gemstone-grade specimen.
Geological facts
Quartzite often preserves faint original sedimentary layering while developing a fused, sugar-like texture. Unlike marble, it does not readily react with dilute hydrochloric acid.
Field identification & locations
Common in metamorphic mountain belts and derived gravels worldwide; likely field tests are a glass-scratch test, examining interlocking quartz grains, and checking for weak or absent bedding and cleavage. Exact identification is less certain because the image shows a mixed, weathered rock pile.
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