Orbicular granite

Scientific Name: Orbicular granite
Image Number: ROM2004_1037_11

This rare form of granite occurs as small bodies within large masses of typically equigranular granite. The spherical to ellipsoidal shapes are made up of the same minerals found in the main body of granite but they are concentrated in concentric layers. A number of theories have been proposed to account for the growth of these unusual “orbs”, “orbicules” or “spherules”. It is much sought after as a building or decorative stone because of its rarity and beauty.