igneous
Polished orbicular granite
Orbicular granite, commonly quartz–feldspar–biotite granite with orbicules
AI-generated identification · may be incorrectTypically Mohs 6–7, orange to salmon from potassium feldspar, dark green-black from biotite, amphibole, or chlorite, with a granular crystalline texture and vitreous to polished luster. Massive, with no cleavage as a whole; feldspar crystals may show cleavage.
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Physical properties
Typically Mohs 6–7, orange to salmon from potassium feldspar, dark green-black from biotite, amphibole, or chlorite, with a granular crystalline texture and vitreous to polished luster. Massive, with no cleavage as a whole; feldspar crystals may show cleavage.
Formation & geological history
A coarse-grained intrusive igneous rock formed by slow cooling of silica-rich magma deep in the crust, likely with orbicules produced by rhythmic mineral growth around nuclei. Most examples formed during ancient Precambrian to Paleozoic plutonic events, depending on locality.
Uses & applications
Used as polished decorative stone, cabochons, tabletops, bookends, and collectible specimens; less commonly as architectural or construction stone.
Geological facts
The rounded dark-and-orange patterns are orbicules or mineral-rich aggregates, not fossils. The glossy surface indicates human polishing, which is still a geological specimen.
Field identification & locations
Identify it by its coarse interlocking crystals, salmon-orange feldspar, dark mafic minerals, and rounded orbicular pattern; distinguish it from breccia by the crystalline, non-fragmental texture. Notable orbicular granites occur in Finland, Madagascar, South Africa, and Australia.
