#orbicular granite

Locality: Mt Polley, British Columbia

Here is Cutesaurus posing on a cube of orbicular granite.

A big cube of orbicular granite at the University of Oxford Museum of Natural History.  Would like to own.

Orbicular granite outcrop near Springbok Northern Cape.  This is probably formed through nucleation around a grain in a cooling magma  chamber and  the rocks  here are said to be  formed approximately one billion years ago.

Granites, by definition, are an intrusive igneous rock formed by melting of crustal material. With a mineralogy identical to a typical granite, orbicular granites differ in their distinctive texture. Only found in a handful of small localities worldwide, it is a very rare example and as such, little is understood about their formation. The main theory suggests that the circles are caused by nucleation around an initial mineral grain as the magma cools in the underground melt chamber. 

look it up.