igneous
Tumbled orbicular granite or granitic gneiss
Granite, chiefly quartz–feldspar–biotite/amphibole; exact variety uncertain from the image
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pale gray-green and black mottling, granular texture, and dull to slightly vitreous luster. The rounded, smooth surface indicates tumbling or polishing; no obvious cleavage is visible.
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Physical properties
Hardness about 6–7 Mohs; pale gray-green and black mottling, granular texture, and dull to slightly vitreous luster. The rounded, smooth surface indicates tumbling or polishing; no obvious cleavage is visible.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep in the crust, generally during Precambrian to Phanerozoic intrusive events; if foliated internally, it may instead be metamorphic gneiss.
Uses & applications
Used as a decorative stone, paperweight, cabochon, or collectible; granite is also widely used for countertops, monuments, aggregate, and building stone.
Geological facts
The black-and-white pattern likely reflects contrasting dark mafic minerals and light feldspar/quartz, rather than true crystal banding. Image-based identification cannot reliably distinguish granite from related gneiss or diorite.
Field identification & locations
Look for interlocking visible grains, abundant pale feldspar/quartz, and black biotite or amphibole; granite has no reaction to dilute acid and is much harder than glass or steel scratches may suggest. Common worldwide, including India, Brazil, Scandinavia, Canada, and the United States.
