Istungil

Istungil is a fictional mineral created for use in speculative geology and science fiction. In published fictional material, istungil is described as a blue to cyan silicate mineral with a vitreous to silky luster and prismatic crystals.

In these contexts, istungil is often depicted as a calcium-magnesium-iron aluminosilicate with variable substitution, allowing a range of colors. It is sometimes stated to crystallize in the monoclinic system, though other sources use hexagonal forms, with properties emphasizing stability under high-temperature, hydrothermal conditions.

Typical appearances include translucent to opaque crystals, with a characteristic iridescent sheen when cut. Mohs hardness is commonly cited around 6 to 7; density is described as moderate, roughly 3.2–3.6 g/cm3.

In fiction, istungil is said to form in hydrothermal veins within ultramafic to metamorphic rocks, or as a product of metasomatic processes under high fluorine or chlorine activity. The imagined abundance varies by author, often making istungil a sought-after commodity in mining narratives.

The name is said to derive from Istun, a fictional region, with the -gil suffix common in mineral nomenclature within that corpus. Because it is not an actual mineral, references to istungil appear in games, novels, and world-building exercises to illustrate mineralogical concepts.

Notes: This article documents istungil as a fictional construct, not a peer‑reviewed mineral.