rauntímis

Rauntímis is a fictional mineral term appearing in speculative geology and worldbuilding. It is described as a rare luminescent oxide-silicate mineral that forms under high-grade metamorphic conditions and is often depicted with shifting iridescence.

The name rauntímis is drawn from constructed language roots used by various authors, with the accent on í commonly appearing in worldbuilding glossaries that feature the term.

In most renderings, rauntímis crystallizes in the monoclinic system and presents as prismatic to tabular crystals. It is typically blue to violet with a metallic to vitreous luster and a pale gray streak. Hardness is reported around 5.5–6.5 on the Mohs scale, and its specific gravity is high, reflecting a dense oxide composition. It is described as fluorescent or phosphorescent, emitting pale blue light under ultraviolet radiation.

In fiction, rauntímis is said to form in ultrahigh-temperature metamorphic rocks and metasomatic zones within basaltic crust, occasionally in xenoliths carried by volcanic eruptions. The most frequently cited locality is the fictional Lumen Basin.

The mineral was introduced in worldbuilding circles as a plot device and subject of mineralogical curiosity. It figures in speculative economies for its perceived beauty and luminescent properties, and is imagined as a collectible gemstone within various cultures.