chromaatanion

Chromaatanion is a term used in materials science and mineralogy to denote a hypothetical color-bearing mineral phase and its related chemical compounds. In theoretical models, chromaatanion compounds embed chromophore centers within a crystalline lattice, producing vivid hues through selective electronic transitions.

The name derives from chroma, meaning color, and from elements of the lattice framework used in proposed structures.

Proposed structures include frameworks related to aluminosilicates or oxide spinels, where transition-metal ions such as chromium, copper, or iron substitute into octahedral or tetrahedral sites. In these models, color arises from crystal field effects and intervalence charge transfer between neighboring metal centers.

As of now, chromaatanion remains hypothetical. No natural specimens have been confirmed, and syntheses reported in the literature are theoretical or preliminary and have not produced a reproducible, well-characterized phase.

In theoretical treatments, chromaatanion is described as having a relatively high refractive index and strong visible absorption bands, leading to intense coloration. Some models also explore potential luminescent or nonlinear optical responses under specific excitations.

See also: color centers; crystal field theory; chromophore; spinel; silicate minerals.