idiochromatic

Idiochromatic is a term used in mineralogy to describe minerals that possess intrinsic color due to the presence of elements that are part of their fundamental chemical composition. These coloring elements are essential to the mineral's structure, meaning they are not impurities or trace elements. The color observed in idiochromatic minerals is a direct consequence of the electronic structure of these essential chromophores. Examples of idiochromatic minerals include malachite, which derives its green color from copper, and azurite, which gets its blue hue from copper as well. Other examples include cinnabar (mercury sulfide) which is red, and realgar (arsenic sulfide) which is orange. The color is typically a consistent and characteristic property of the mineral species, though slight variations can occur due to differences in crystal structure or oxidation state of the coloring elements. This contrasts with allochromatic minerals, whose color arises from impurities or defects in their crystal lattice.