Alabaster and Derbyshire or satin spar are extra fine grades of gypsum, not always pure white, and chiefly used for making ornaments. Satin spar especially comes in long, fibrous pieces. Selenite is another form of gypsum, large blocks of which may be found in the Rocky Mountains and the Indian Territory. The material is not hard, but transparent and will cleave like mica, but while mica will stand heat, selenite falls into a white powder under its influence. Is not a good form of gypsum for oil paint, but will serve the purpose of a white pigment for water paint when first heated and powdered.