The Collaborative International Dictionary
Castorite
Castor \Cas"tor\, Castorite \Cas"tor*ite\, n. [The minerals castor and pollux were so named because found together on the island of Elba. See Castor and Pollux.] (Min.) A variety of the mineral called petalite, from Elba.
Wiktionary
castorite
n. (context mineral English) castor