metamorphic
Weathered quartz-rich metamorphic rock, possibly quartzite
Quartzite (SiO₂-rich metamorphic rock), with probable feldspar, mica, and iron-oxide staining
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; mottled tan, brown, gray, and cream; earthy to slightly vitreous luster. Crystalline granular texture, generally lacking cleavage, with rough weathered surfaces and possible iron-oxide patches.
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Physical properties
Hardness about 6.5–7 Mohs; mottled tan, brown, gray, and cream; earthy to slightly vitreous luster. Crystalline granular texture, generally lacking cleavage, with rough weathered surfaces and possible iron-oxide patches.
Formation & geological history
Likely formed when quartz-rich sandstone recrystallized under heat and pressure during regional metamorphism; age cannot be determined from the photograph and may range from Precambrian to younger. The rusty coloration commonly results from weathering of iron-bearing minerals.
Uses & applications
Used as crushed aggregate, road stone, building stone, and occasionally decorative stone; attractive specimens may be collected but this piece appears common and unpolished.
Geological facts
Quartzite commonly breaks across grains rather than around them and is typically harder than ordinary sandstone. The dark cavity and uneven surface may also indicate a quartz-rich metamorphic rock with minor sulfide or mica minerals.
Field identification & locations
Test whether it scratches window glass or a steel file; a fresh broken surface should look sugary and quartz-rich. Common in metamorphic mountain belts worldwide, including the Appalachians, Rocky Mountains, India, Brazil, and Scandinavia.
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