| Igneous Rock | |
Polished rock sample of orbicular granite from Mount Magnet, Western Australia. |
|
| Composition | |
|---|---|
| Granitic |
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. Almost one third of known orbicular rock occurrences are from Finland.[1] The occurrences are usually very small.[2]