ceruleum

Century Dictionary and Cyclopedia

1. n. A blue pigment, consisting of stannate of protoxid of cobalt, mixed with stannic acid and sulphate of lime. Ure, Dict. Also spelled cæruleum.

GNU Webster's 1913

1. n. A greenish blue pigment prepared in various ways, consisting essentially of cobalt stannate. Unlike other cobalt blues, it does not change color by gaslight.