metamorphic
Weathered quartz-rich rock, possibly chert or quartzite fragment
Indeterminate; likely microcrystalline quartz (SiO₂), possibly with iron-oxide staining
AI-generated identification · may be incorrectGray-brown, opaque to slightly translucent, with a dull to waxy luster and irregular fracture; visible hardness is likely about 6.5–7 Mohs, with no obvious cleavage. The rounded surface suggests natural abrasion or weathering.
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Physical properties
Gray-brown, opaque to slightly translucent, with a dull to waxy luster and irregular fracture; visible hardness is likely about 6.5–7 Mohs, with no obvious cleavage. The rounded surface suggests natural abrasion or weathering.
Formation & geological history
Likely formed from silica-rich sediment that lithified and/or recrystallized, then became weathered and rounded; precise geological age and rock identity cannot be determined from the photograph. Iron oxides may account for the brown coloration.
Uses & applications
Common material of this type is used as aggregate, road stone, abrasives, and occasionally as a lapidary or teaching specimen; it has little jewelry value unless confirmed as attractive chert, jasper, or quartzite.
Geological facts
Quartz-rich rocks commonly resist weathering and survive as rounded pebbles. A steel nail should not scratch it, while it may scratch ordinary glass.
Field identification & locations
Look for a glassy or waxy silica-rich fracture, absence of carbonate fizz with dilute acid, and hardness near 7; a streak, specific-gravity test, and magnification would improve identification. Common in river gravels, glacial deposits, and weathered silica-rich bedrock.
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