POLLUCITE
pollucite
(noun) a rare mineral that is an important source of cesium
Source: WordNet® 3.1
Etymology
Noun
pollucite (plural pollucites)
(mineral) A colorless transparent mineral of the zeolite family consisting of hydrous cesium aluminum silicate and occurring massive or crystallizing in cubes.
Source: Wiktionary
Pol"lu*cite, n. Etym: [See Pollux, and 4th Castor.] (Min.)
Definition: A colorless transparent mineral, resembling quartz, occurring
with castor or castorite on the island of Elba. It is a silicate of
alumina and cæsia. Called also pollux.
Source: Webster’s Unabridged Dictionary 1913 Edition