(id'-i-o-chro-ma-tic) Color is inherent and due to some aspect of the chemical composition and crystal structure. Idiochromatic is the opposite of allochromatic.

Describes gems whose colour is due to elements that are an essential part of the chemical composition.

Exhibiting only a single color. Minerals that are monochromatic occur in only one color, no matter what specimen. Same as monochromatic.