igneous
Orbicular Gabbro
Orbicular Gabbro
Hardness of 6-7 on the Mohs scale; distinctive orbicular or spheroidal texture with concentric alternating light (plagioclase feldspar) and dark (pyroxene/amphibole) mineral rings; vitreous to dull luster; specific gravity around 2.9-3.1.
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Physical properties
Hardness of 6-7 on the Mohs scale; distinctive orbicular or spheroidal texture with concentric alternating light (plagioclase feldspar) and dark (pyroxene/amphibole) mineral rings; vitreous to dull luster; specific gravity around 2.9-3.1.
Formation & geological history
Forms through complex magmatic processes involving slow cooling and crystallization under specific geochemical conditions in intrusive mafic igneous bodies, often deep within the Earth's crust.
Uses & applications
Used primarily as a decorative ornamental stone, in lapidary arts for cabochons and polished specimens, and highly prized by rock and mineral collectors.
Geological facts
Orbicular rocks are relatively rare geological formations, and orbicular gabbro (sometimes marketed commercially as naplesite or corsite) is particularly famous for its striking polka-dot or target-like patterns.
Field identification & locations
Easily identified by the characteristic rounded, concentric ring structures visible on cut or weathered surfaces; commonly found in specific localized occurrences globally, such as in Corsica, Finland, and parts of North America.
