metamorphic
Iron-stained quartzite or quartz-rich metamorphic rock
Quartzite, predominantly SiO₂, with iron-oxide coatings (goethite/hematite)
AI-generated identification · may be incorrectHardness about 7 Mohs; gray to rusty orange-brown, with a dull to slightly vitreous luster and massive, interlocking quartz texture. It lacks obvious cleavage and breaks irregularly; the rusty colors reflect iron oxides along fractures or layering.
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Physical properties
Hardness about 7 Mohs; gray to rusty orange-brown, with a dull to slightly vitreous luster and massive, interlocking quartz texture. It lacks obvious cleavage and breaks irregularly; the rusty colors reflect iron oxides along fractures or layering.
Formation & geological history
Likely formed when quartz-rich sandstone was metamorphosed and recrystallized under heat and pressure, later weathered and oxidized by groundwater. Its exact geological age cannot be determined from the photograph.
Uses & applications
Used as crushed stone, road aggregate, building and facing stone, and occasionally as a decorative lapidary material. This specimen has limited jewelry value unless it displays unusually attractive banding or polish.
Geological facts
Quartzite commonly preserves sedimentary layering while becoming much harder than its sandstone precursor. Iron oxidation can produce vivid yellow, orange, and red staining without making the rock an iron ore.
Field identification & locations
Identify it by testing whether grains fracture through the rock rather than separating around them, and by its resistance to scratching; quartz should scratch glass. Common in metamorphic mountain belts worldwide, including the Appalachians, Rocky Mountains, Alps, and Scandinavian Shield.
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