The Collaborative International Dictionary
Tysonite
Tysonite \Ty"son*ite\, n. [After S. T. Tyson.] (Min.) A fluoride of the cerium metals occurring in hexagonal crystals of a pale yellow color. Cf. Fluocerite.
Wiktionary
tysonite
n. (context mineralogy English) A fluoride of the cerium metals occurring in pale yellow hexagonal crystals.