A gemstone is idiochromatic when the element causing its color is an essential part its chemical composition. For example, iron, which is an intrinsic part of the chemical makeup of peridot, is the cause of its green color.
having unique or distinctive coloration
Exhibiting only a single color. Minerals that are monochromatic occur in only one color, no matter what specimen. Same as monochromatic.
idiochromatic Having a distinctive and constant coloration, used especially of minerals.
Refers to minerals that are always the same colour. i.e. Malachite is always green, Azurite is always blue and Sulphur is always yellow.
(of a mineral) deriving a characteristic color from its capacity to absorb certain light rays. Cf. allochromatic.