Definition of star stone in US English:

star stone

noun

  • 1Any of the pentagonal or star-shaped stem ossicles of fossil pentacrinites.

  • 2A gemstone which exhibits asterism; especially a star sapphire.

Origin

Mid 17th century; earliest use found in Thomas Nicols (fl. 1652), writer on gemstones. From star + stone.

Pronunciation

star stone

/ˈstɑː stəʊn/