igneous
Polished orbicular/porphyritic granite or breccia
Likely potassium-feldspar–quartz granite with amphibole/biotite and epidote; exact variety uncertain from the image
AI-generated identification · may be incorrectCoarse, multicolored interlocking crystals and dark green-black matrix; pink areas are K-feldspar, pale blue-gray areas likely quartz or feldspar, and green-black minerals likely amphibole, biotite, or epidote. Hardness is roughly 6–7, with vitreous to dull luster and no obvious cleavage on the polished surface.
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Physical properties
Coarse, multicolored interlocking crystals and dark green-black matrix; pink areas are K-feldspar, pale blue-gray areas likely quartz or feldspar, and green-black minerals likely amphibole, biotite, or epidote. Hardness is roughly 6–7, with vitreous to dull luster and no obvious cleavage on the polished surface.
Formation & geological history
Formed by slow crystallization of silica-rich magma, possibly with later fracturing and hydrothermal alteration producing the green matrix; generally Precambrian to Paleozoic in age depending on locality.
Uses & applications
Used as a decorative polished stone, cabochon, sphere, and ornamental object; rarely used as architectural granite because of its irregular texture.
Geological facts
The rounded shape and strong polish are human-processed, but the material remains a geological specimen. Its exact trade name may be marketed as orbicular granite, jasper-granite, or an epidote-bearing granite.
Field identification & locations
Identify by coarse crystal size, pink feldspar, gray quartz, and green-black mafic minerals; a streak, hardness, acid, and thin-section test would distinguish granite from breccia or jasper. Similar rocks occur in Finland, Madagascar, India, Canada, and the western United States.
