orbicular granite
英[ɔ:ˈbikjulə ˈɡrænit]美[ɔrˈbɪkjəlɚ ˈɡrænɪt]
Orbicular granite (also known as orbicular rock or orbiculite) is an uncommon plutonic rock type which is usually granitic in composition. These rocks have a unique appearance due to orbicules - concentrically layered, spheroidal structures, probably formed through nucleation around a grain in a cooling magma chamber.