Answer: cyanite

AnswerCrossword Clue
cyanitemineral, aluminum silicate, Al2SiO5, occurring in blue or greenish bladed triclinic crystals, used as a refractory
cyanitea mineral, also KYANITE
cyanitean aluminum silicate mineral Al2SiO5 that occurs usually in blue thin-bladed triclinic crystals and crystalline aggregates