metamorphic
Iron-rich quartzite or ferruginous metamorphic rock
Quartzite, predominantly SiO₂, stained by iron oxides (hematite/goethite)
AI-generated identification · may be incorrectHardness about 7 Mohs; rusty brown to golden-brown, earthy to slightly silky luster, massive granular texture, and no obvious cleavage. The pale white patches are likely quartz; iron-oxide staining produces the orange-brown color and may give a relatively high specific gravity.
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Physical properties
Hardness about 7 Mohs; rusty brown to golden-brown, earthy to slightly silky luster, massive granular texture, and no obvious cleavage. The pale white patches are likely quartz; iron-oxide staining produces the orange-brown color and may give a relatively high specific gravity.
Formation & geological history
Formed when quartz-rich sandstone was recrystallized under heat and pressure, later weathered and stained by oxidized iron. The precise age cannot be determined from the photograph; such rocks occur in many Precambrian and younger mountain belts.
Uses & applications
Used as durable crushed stone, aggregate, building stone, and occasionally as an ornamental or lapidary material. This rough specimen has limited commercial value unless it comes from a notable locality.
Geological facts
Quartzite commonly rings when struck and resists scratching by steel, while iron staining can make it resemble limonite-rich rock or jasper. Strong acid should not fizz unless carbonate minerals are present.
Field identification & locations
Common in metamorphic terrains, especially former sandstone belts worldwide. Confirm with a scratch test, streak test, and close examination for interlocking quartz grains; a definitive identification may require thin-section or chemical analysis.
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