Egyptian Blue is a synthetic blue pigment made up of a mixture of silica, lime, copper, and alkali. Its color is due to a calcium-copper tetrasilicate CaCuSi4O10 of exactly the same composition as the naturally occurring mineral cuprorivaite. It occurs in Egypt during the third millennium BC and is the first synthetic pigment to have been produced there, continuing in use until the end of the Greco-Roman period (332 BC–395 AD)