igneous
Weathered red-brown granite or granitic gneiss pebble
Feldspar–quartz–mica aggregate; likely altered granite, possibly gneiss
AI-generated identification · may be incorrectHardness about 6–7 Mohs; reddish-brown, fine- to medium-grained, dull to weakly subvitreous luster, with apparent quartz/feldspar grains and iron-oxide staining. Massive and rounded by abrasion; no obvious cleavage as a whole rock.
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Physical properties
Hardness about 6–7 Mohs; reddish-brown, fine- to medium-grained, dull to weakly subvitreous luster, with apparent quartz/feldspar grains and iron-oxide staining. Massive and rounded by abrasion; no obvious cleavage as a whole rock.
Formation & geological history
Likely formed by slow crystallization of felsic magma deep underground, then weathered and transported in a stream or glacial deposit. Granite commonly formed hundreds of millions to billions of years ago, but this individual pebble’s age cannot be determined from the image.
Uses & applications
Granite is widely used as crushed stone, aggregate, paving, countertops, monuments, and building stone; an ordinary rounded specimen has little commercial value.
Geological facts
The rusty red color commonly comes from oxidation of iron-bearing minerals or staining along fractures. A polished or freshly broken surface would better reveal quartz, feldspar, and mica proportions.
Field identification & locations
Look for interlocking grains, visible glassy quartz, pink/white feldspar, and occasional dark mica; a streak test is generally unhelpful. Common in continental crust and river, beach, and glacial gravels.
