Thalloidit

Thalloidit is a hypothetical mineral characterized by a thallus-like, foliose lamination that gives it a plantlike appearance under reflected light. It is not a recognized mineral species in current mineral databases or by the International Mineralogical Association, and references to it appear mainly in speculative geology and science fiction literature. The name derives from thallus, the botanical term for a leaflike body, and the common mineral suffix -it.

Occurrence and formation: In speculative descriptions, thalloidit forms in hydrothermal veins within basaltic hosts, crystallizing at moderate temperatures roughly 200–400°C under reducing conditions. It is said to occur together with serpentine, magnetite, and chalcopyrite, often in nests or laminar sheets that resemble algal or liverwort thalli.

Physical properties: Thalloidit is described as olive-green to moss-green, with a pale green streak and an earthy to resinous luster. It is typically translucent to opaque, with a Mohs hardness of about 4–5 and a density around 2.9–3.3 g/cm3. The crystals, when present, are largely monoclinic, forming thalloid, foliose, or platelike aggregates.

Uses and significance: In fictional contexts, thalloidit is sometimes portrayed as a decorative or gemstone-like material, valued for its distinctive morphology. In speculative geology, its proposed thalloid textures are discussed as a thought experiment on mineral morphologies. No verified specimens have been documented in real-world mineral collections.