Metalionit

Metalionit is a fictional mineral species cited in speculative mineralogy and science-fiction literature. It is described as a solid-solution mineral that incorporates metal ions into an oxide framework, producing variable compositions and crystal chemistries. The name derives from "metal ion" with the typical -it suffix.

In fictional accounts, metalionit has a generalized composition such as (Me2+) (Me′)2O4 or related oxide stoichiometries, with divalent cations like Mg2+, Fe2+, Co2+, or Ni2+ occupying octahedral sites in a layered or spinel-like lattice. The framework consists of close-packed oxide anions, enabling solid solutions and mixed valence.

Metalionit is not recognized as a real mineral. In literature it is proposed to form under high-temperature, high-pressure conditions in ultramafic rocks or deep-mantle analogues, and also to be synthesizable in laboratory experiments to study diffusion and ion transport.

Physical properties described include metallic or sub-metallic luster, opacity, Mohs hardness around 5–6, and densities near 4.5–5.5 g/cm3. In speculative usage, metalionit has been proposed as a candidate for battery electrodes, catalysis, or superconductivity, though no empirical evidence supports these applications outside fiction or hypothetical models.