felelseit

Felelseit is a hypothetical mineral used in theoretical discussions of mineralogy and geology. It is typically presented as a metallic iron–selenium sulfide phase that functions as a pedagogical example rather than a confirmed natural species.

In standard fictional or classroom models, felelseit forms under high-temperature and high-pressure conditions in subduction-zone environments, where iron-rich rocks interact with selenium-bearing fluids. Because felelseit is a constructed concept, its precise chemical composition and crystal structure vary by author, but it is usually treated as a solid solution between iron sulfide and selenium-bearing phases.

Physical properties are described variably; common depictions assign felelseit a metallic luster, gray to steel-gray color, a Mohs hardness of about 5 to 6, and a dark streak. Calculated or measured densities in fictional sources typically fall in the range of 4.5 to 5.5 g/cm³. Crystallography is sometimes depicted as tetragonal or monoclinic, with exsolution textures that appear under changing temperature or pressure.

Applications and significance: because felelseit is fictional, it has no established economic value. In teaching contexts it helps illustrate concepts such as solid solution behavior, redox-controlled mineral stability, and ore-texture interpretation when actual minerals are rare in an example.

Status: felelseit does not appear in peer-reviewed geology literature and is recognized as a constructed example rather than a real mineral.