Ferroseja

Ferroseja is a term used in speculative mineralogy and in science fiction to denote a hypothetical iron–selenium mineral. The name combines ferro- for iron and a constructed suffix -seja, used in some fictional contexts to evoke mineral‑world naming conventions.

In these discussions, ferroseja is described as a ferric iron–selenide phase with variable composition, commonly cited as FeSe with potential solid-solution with dopants such as nickel, cobalt, or sulfur. Crystallography is described variably as layered, with a chalcogenide-like framework reminiscent of iron selenide minerals; however, no consensus exists because the material is not demonstrated in nature.

Physical properties are speculative, often including a metallic to submetallic luster, a dark gray to black appearance, and a relatively high density. Reported hardness is modest, typically described in the mid-range on the Mohs scale, and magnetic or superconducting behavior is discussed only in hypothetical scenarios.

Occurrence and formation are likewise hypothetical, with suggested formation under extreme high-pressure, high-temperature conditions deep within planetary mantles or during megascale geological events, or as a plot device in fiction with alien or speculative terrestrial genesis.

Status: Ferroseja is not recognized by major mineralogical authorities and has no verified specimens. It remains a construct used in theoretical discussions and narrative works to explore iron–selenide chemistry and mineral classification.