igneous
Blue-gray quartz-rich pebble, possibly granite or granodiorite
Quartz–feldspar–mica aggregate; likely granodiorite (exact identification requires testing)
AI-generated identification · may be incorrectFine- to medium-grained, blue-gray, dull to weakly vitreous luster with pale grains and dark specks; individual crystals are interlocking. Estimated hardness 6–7 overall, with no obvious cleavage; specific gravity about 2.65–2.75.
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Physical properties
Fine- to medium-grained, blue-gray, dull to weakly vitreous luster with pale grains and dark specks; individual crystals are interlocking. Estimated hardness 6–7 overall, with no obvious cleavage; specific gravity about 2.65–2.75.
Formation & geological history
Likely an eroded fragment of intrusive igneous rock crystallized slowly from magma deep in the crust, commonly Paleozoic to Precambrian in age depending on source region. Its rounded shape reflects transport by stream, glacier, or beach processes.
Uses & applications
Commonly used as aggregate, road stone, landscaping material, and building stone; this small specimen has little jewelry value unless it proves to be a rarer blue mineral-bearing rock.
Geological facts
The blue-gray color may come from quartz, altered feldspar, or minor sodic amphibole rather than a single blue mineral. A fresh broken surface and magnification would substantially improve identification.
Field identification & locations
Look for visible quartz, white/gray feldspar, and black mica or amphibole in a granular texture; a glass-scratch test and streak testing individual grains can help. Common worldwide in granitic terrains and gravel deposits.
