water sapphire

English Thesaurus

1. a deep blue cordierite often used as a gemstone (noun.substance)

hypernym	:	cordierite,
definition	:	a blue mineral of magnesium and iron and aluminum and silicon and oxygen; often used as a gemstone (noun.substance)

hypernym	:	transparent gem,
definition	:	a gemstone having the property of transmitting light without serious diffusion (noun.substance)