metamorphic
Weathered quartz-rich metamorphic rock (probable quartzite)
Quartzite; predominantly crystalline SiO₂, possibly iron-oxide stained
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray, cream, tan, and rusty brown with a dull to sugary vitreous luster. Massive, interlocking quartz grains and no obvious cleavage; iron oxides produce the yellow-brown staining.
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Physical properties
Hardness about 7 Mohs; pale gray, cream, tan, and rusty brown with a dull to sugary vitreous luster. Massive, interlocking quartz grains and no obvious cleavage; iron oxides produce the yellow-brown staining.
Formation & geological history
Formed when quartz-rich sandstone was deeply buried and recrystallized during metamorphism, commonly during mountain-building events hundreds of millions to billions of years ago. Surface weathering caused the rusty coloration and rough rind.
Uses & applications
Used as crushed aggregate, riprap, building stone, and occasionally decorative slab; attractive pieces may be collected but this specimen appears ordinary.
Geological facts
Quartzite commonly breaks across grains rather than around them, unlike weak sandstone. A steel nail should not scratch fresh quartzite, while the rock may scratch glass.
Field identification & locations
Likely quartzite if fresh broken surfaces are sparkly and uniformly hard; sandstone, ironstone, or weathered vein material remain alternatives without a close-up or locality. Common in uplifted mountain belts worldwide.
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