castorite
noun
cas·tor·ite
ˈkastəˌrīt,
-ˈaa-,
-ˈai-,
-ˈȧ-
variants or castor
-tə(r) 
plural -s
: a mineral consisting of a variety of petalite occurring in transparent crystal
Word History
Etymology
castorite from German kastor (from Kastor mythological personage, from Latin Castor) + English -ite; castor from German kastor; from its appearance with pollucite (previously called pollux)