Pollux
a celebrated hero of the Grecian mythology, and twin brother of Castor, after whose death he implored Jupiter to render him immortal. His prayer could not be entirely granted, but Jupiter divided immortality between the brothers, each living and dying alternately. In astronomy, one of the twins forming the constellation Gemini. Also the name of a star of the second magnitude in the same constellation. In mineralogy, a hydrated silicate of alumina, potash, and soda, remarkable for containing 34 per cent. of cæsium. It is a rare mineral.