pollucite
/ˈpɒl(j)ʊsʌɪt/ /pəˈljuːsʌɪt/Mineralogy
noun
A rare mineral of the cubic crystal system which consists of a hydrated aluminosilicate of caesium and sodium, (Cs,Na)2Al2Si4O12·H2O, occurring as transparent colourless crystals, especially in pegmatites, and used as a gemstone.
Origin
Mid 19th century; earliest use found in James Dana (1813–1895), geologist, zoologist, and teacher. From classical Latin Pollūc-, Pollūx + -ite, after German Pollux, so named on account of its having been first discovered in association with the similar mineral Castor.