igneous
Polished orbicular granite (likely K2-type granite)
Granite; chiefly quartz (SiO₂), alkali feldspar/plagioclase, biotite/amphibole, with dark orbicules possibly riebeckite or amphibole minerals
AI-generated identification · may be incorrectCoarse-grained, mottled pink, gray, black, cream, and green; vitreous quartz and feldspar luster, massive texture, no strong cleavage as a whole, Mohs hardness about 6–7, specific gravity roughly 2.6–2.8. The rounded shape and smooth surface indicate tumbling or polishing.
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Physical properties
Coarse-grained, mottled pink, gray, black, cream, and green; vitreous quartz and feldspar luster, massive texture, no strong cleavage as a whole, Mohs hardness about 6–7, specific gravity roughly 2.6–2.8. The rounded shape and smooth surface indicate tumbling or polishing.
Formation & geological history
A slowly cooled intrusive igneous rock formed deep in the continental crust, generally of Paleozoic to Mesozoic age depending on locality. Orbicular varieties develop unusual concentric mineral textures during late-stage magma crystallization or fluid alteration.
Uses & applications
Used as a lapidary stone for cabochons, carvings, polished stones, and decorative objects; not commonly used structurally because the specimen is ornamental.
Geological facts
The colorful dark-centered orbs and pink feldspar are characteristic of orbicular granite, while “K2 granite” is a popular trade name for a blue-spotted variety from Pakistan; this specimen may be a related orbicular type rather than verified K2 granite.
Field identification & locations
Identify it by its interlocking coarse crystals, abundant pink feldspar, gray quartz, black amphibole/biotite, and orbicular pattern; unlike marble, it lacks a sugary calcite texture and usually does not fizz in dilute acid. Common sources include Pakistan, Finland, Madagascar, and other granite provinces.
