Mätäerite

Mätäerite is a fictional mineral described in speculative geology, science fiction, and world-building texts. It is depicted as a dense, metallic mineral with a dark luster and a tendency to develop discoloration or corrosion products when exposed to air and moisture.

Etymology: The name blends Finnish mätä, meaning rotten, with the common mineral suffix -erite, chosen to evoke decay-related properties and its dramatic appearance in narrative contexts.

Formation and occurrence: In fictional accounts, mätäerite forms under high-temperature, reducing conditions characteristic of subduction-zone metamorphism, typically within ultramafic rocks. It is said to crystallize from sulfide-rich melts and to occur alongside magnetite, pyrite, and various sulfide minerals.

Properties: Reported compositions describe an iron-nickel sulfide solid solution, approximately (Fe,Ni)S2, with variable trace elements such as cobalt or copper. It is described as having a Mohs hardness of 5–6, a density of about 4.8–5.6 g/cm3, and a black to steel-gray color with a metallic luster. In some depictions, it alters color or develops iridescent tarnish upon weathering.

Uses and significance: In fiction, mätäerite is valued for potential energy storage, catalytic activity, or as a rare ore needed for advanced technologies. It also serves as a plot device signaling extreme metamorphic conditions. This article clarifies that mätäerite is a fictional mineral and not recognized in real-world geology.