Asterism is more commonly known as the 'star' phenomenon, with the most prized examples occurring in sapphires and rubies. It can, however, also appear in spinel, diopside, beryl, and quartz. This phenomenon is caused by tiny needle like inclusions which reflect light onto the surface of the stone.
This vintage ring features a lovely, berry pink star ruby flanked by 2 diamonds (.06 ctw) set in 14k gold. Currently a size 6.75 and sizable.