igneous
Polished orbicular granite (likely orbicular diorite)
Orbicular granitoid; chiefly quartz, feldspar, and dark amphibole/biotite
AI-generated identification · may be incorrectRounded, polished specimen with cream-gray matrix and black-green mottled inclusions. Likely hardness 6–7 Mohs, vitreous to dull luster, massive granular texture, no obvious cleavage on the surface; density roughly 2.6–2.9 g/cm³.
Identified More igneous →
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Physical properties
Rounded, polished specimen with cream-gray matrix and black-green mottled inclusions. Likely hardness 6–7 Mohs, vitreous to dull luster, massive granular texture, no obvious cleavage on the surface; density roughly 2.6–2.9 g/cm³.
Formation & geological history
A coarse intrusive igneous rock formed when magma cooled slowly underground; the orbicular patterns reflect concentric mineral growth around nuclei during crystallization. Its exact geological age cannot be determined visually.
Uses & applications
Used mainly as a decorative stone, polished sphere, and collector specimen; not usually an especially valuable gemstone.
Geological facts
The dark patches are probably biotite or hornblende, while pale areas are feldspar and possibly quartz. Orbicular rocks are uncommon and their patterns can resemble leopard skin.
Field identification & locations
The rounded shape and uniform polish indicate human shaping, but it remains a geological specimen. Near 38.4°N, 84.4°W, local bedrock is mainly sedimentary, so this was likely imported or a commercial polished stone rather than locally formed rock; confirm with a magnet, streak, and close inspection for quartz/feldspar grains.
