metamorphic
Weathered quartz-rich stone, likely chert or quartzite
Quartzite (recrystallized SiO₂) or microcrystalline quartz (chert)
AI-generated identification · may be incorrectHardness about 7 Mohs; tan to ochre with gray, white, and rusty iron-oxide patches, earthy-to-waxy luster, massive texture, and no obvious cleavage. The rounded shape and smooth surface indicate water or abrasive weathering.
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Physical properties
Hardness about 7 Mohs; tan to ochre with gray, white, and rusty iron-oxide patches, earthy-to-waxy luster, massive texture, and no obvious cleavage. The rounded shape and smooth surface indicate water or abrasive weathering.
Formation & geological history
Likely formed from silica-rich sediment or sandstone, later lithified and possibly metamorphosed; iron oxidation produced the rusty coloration. Exact geological age and origin cannot be determined from the photograph.
Uses & applications
Common quartzite is used as aggregate, building stone, paving material, and occasionally as a decorative or lapidary stone; chert is also used for tools and abrasives.
Geological facts
Quartz-rich rocks commonly resist weathering, leaving rounded pebbles after softer surrounding material erodes. A fresh fracture should appear glassy or granular and may be translucent at thin edges.
Field identification & locations
Look for glassy quartz grains, conchoidal fracture in chert, and a lack of fizz with dilute hydrochloric acid; a steel file should not scratch it easily. Common in stream gravels and quartz-rich mountain regions worldwide.
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