metamorphic
Weathered quartz-rich rock, possibly quartzite or chert
Quartz (SiO₂), likely in a quartzite matrix; exact identification is uncertain from the image
AI-generated identification · may be incorrectTan-brown, opaque to translucent, dull-to-waxy luster with a white granular edge and irregular fracture; quartz hardness is about Mohs 7, with no obvious cleavage. The brown color likely reflects iron-oxide staining or weathering.
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Physical properties
Tan-brown, opaque to translucent, dull-to-waxy luster with a white granular edge and irregular fracture; quartz hardness is about Mohs 7, with no obvious cleavage. The brown color likely reflects iron-oxide staining or weathering.
Formation & geological history
If quartzite, it formed when quartz-rich sandstone was metamorphosed under heat and pressure, commonly during regional mountain-building; if chert, it is sedimentary microcrystalline quartz formed from silica-rich sediments. Geological age cannot be determined visually.
Uses & applications
Ordinary material has little industrial or jewelry value, though quartzite is used as aggregate, building stone, and decorative material; attractive pieces may be collected as curiosities.
Geological facts
The rounded surface and contrasting white granular portion suggest weathering or a broken vein/rock fragment rather than a complete crystal. A steel file should not scratch quartz-rich areas.
Field identification & locations
Common in metamorphic terrains, river gravels, and quartz veins worldwide; test hardness, streak, and acid reaction, and inspect with a hand lens for interlocking quartz grains. A definitive identification requires thin-section or analytical testing.
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