The story
From Pollux + -ite, named after Pollux, the twin of Castor, as it is often found associated with castorite (now petalite).
Etymology from Wiktionary, CC BY-SA 4.0.
pollucite
Today it means: A colorless transparent mineral of the zeolite family consisting of hydrous cesium aluminum silicate and occurring massive or crystallizing in cubes. Full definition →