metamorphic
Iron-stained quartz-rich rock, possibly weathered quartzite
Quartzite (dominantly SiO₂), with iron-oxide staining; identification uncertain from image alone
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray to cream with yellow-brown limonite/goethite staining, vitreous to dull luster, granular interlocking quartz texture, and no obvious cleavage. Dense and resistant, likely scratches glass.
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Physical properties
Hardness about 7 Mohs; pale gray to cream with yellow-brown limonite/goethite staining, vitreous to dull luster, granular interlocking quartz texture, and no obvious cleavage. Dense and resistant, likely scratches glass.
Formation & geological history
Quartzite forms when quartz-rich sandstone is recrystallized under heat and pressure, commonly during regional metamorphism; its age depends on the source formation and cannot be determined visually. Surface oxidation produced the rusty yellow-brown coloration.
Uses & applications
Used as crushed stone, road aggregate, building stone, and occasionally as decorative stone; unattractive or heavily weathered pieces generally have little ornamental value.
Geological facts
Quartzite can resemble quartz-rich sandstone, but recrystallized grains typically form a hard, fused texture that breaks through grains rather than around them.
Field identification & locations
Likely localities include metamorphic belts worldwide, especially India, Brazil, the United States, and Scandinavia. Check for glass-scratching hardness, a streakless white powder, and absence of acid fizz; value is usually about $1–$10 as a common specimen, or $10–$30 if unusually attractive.
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