igneous
Blue-gray quartz-rich rock fragment, likely crushed granite or gneiss
Granite–gneiss aggregate; chiefly quartz (SiO₂), feldspar, and mica/amphibole
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pale blue-gray, white, and dark grains with a vitreous to dull luster. The irregular fracture and visible interlocking mineral grains suggest crystalline silicate rock; cleavage belongs to feldspar/mica rather than the whole specimen.
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Physical properties
Hardness about 6–7 Mohs; pale blue-gray, white, and dark grains with a vitreous to dull luster. The irregular fracture and visible interlocking mineral grains suggest crystalline silicate rock; cleavage belongs to feldspar/mica rather than the whole specimen.
Formation & geological history
Likely an ancient intrusive granite or metamorphosed granitic gneiss, formed deep in the crust and later uplifted, weathered, and crushed. Exact age and identity cannot be determined from the photograph alone.
Uses & applications
Commonly used as road aggregate, landscaping gravel, concrete aggregate, and dimension stone; unattractive fragments have negligible jewelry use.
Geological facts
The blue-gray appearance commonly comes from quartz, plagioclase feldspar, and dark mica or amphibole, sometimes with surface weathering or dust.
Field identification & locations
Identify it by its granular, interlocking texture, hardness, and lack of vesicles or strong layering; a steel nail should not easily scratch it, while quartz grains may scratch glass. Common worldwide, especially in gravel pits and glacial deposits.
