igneous
Iron-stained quartz-rich cobble
Weathered granitic or quartz-feldspar rock; exact identification requires testing
AI-generated identification · may be incorrectHardness approximately 6–7 Mohs, rusty orange-brown from iron-oxide staining, with gray-white quartz/feldspar grains and possible dark mica or mafic inclusions; generally massive, with little visible cleavage and a dull to slightly glassy luster.
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Physical properties
Hardness approximately 6–7 Mohs, rusty orange-brown from iron-oxide staining, with gray-white quartz/feldspar grains and possible dark mica or mafic inclusions; generally massive, with little visible cleavage and a dull to slightly glassy luster.
Formation & geological history
Likely a naturally weathered and water-rounded fragment of granite, granodiorite, or quartz-rich metamorphic rock. Its precise age and source cannot be determined from the photograph; iron minerals oxidized during surface weathering.
Uses & applications
Common material used as aggregate, riprap, landscaping stone, and occasionally as a rough collector specimen; not typically gem-quality.
Geological facts
The orange coloration is usually limonite/goethite coating or staining rather than a distinct orange mineral. A streak test, acid test, and close-grained examination would help distinguish granite from gneiss, quartzite, or iron-rich breccia.
Field identification & locations
Look for interlocking quartz and feldspar grains, hardness sufficient to scratch glass, and no reaction to dilute hydrochloric acid. Common in stream gravels, glacial deposits, and weathered bedrock worldwide.
