metamorphic
Weathered iron-stained quartzite or quartz vein rock
Quartz-rich rock, predominantly SiO₂, with limonite/goethite iron oxides
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; gray to cream quartz with rusty yellow-brown staining, dull to glassy luster, and massive granular texture. No obvious cleavage; the dark areas may be mica or host rock.
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Physical properties
Hardness about 6.5–7 Mohs; gray to cream quartz with rusty yellow-brown staining, dull to glassy luster, and massive granular texture. No obvious cleavage; the dark areas may be mica or host rock.
Formation & geological history
Likely formed when quartz-rich sediment or a silica vein was metamorphosed, then exposed and weathered; iron-bearing fluids produced the ochre staining. A precise geological age cannot be determined from the photograph.
Uses & applications
Common quartzite is used as aggregate, building stone, landscaping material, and occasionally as a decorative specimen. This piece has limited jewelry value unless cutting reveals attractive quartz patterns.
Geological facts
The yellow-brown coloration is typically limonite/goethite, produced by oxidation of iron minerals. Quartzite commonly resists weathering more strongly than surrounding rocks, leaving rounded residual cobbles.
Field identification & locations
Look for a very hard surface that scratches glass and breaks through quartz grains rather than around them; a streak test may show little color, while iron staining leaves a yellow-brown powder. Common in metamorphic terrains and stream gravels worldwide.
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