stillingum

Stillingum is a fictional mineral used in theoretical mineralogy and in speculative fiction to illustrate mineralogical concepts. It is typically represented as a hexagonal silicate, colorless to pale green, with a vitreous luster and a Mohs hardness of 6.5–7. Crystals are described as prismatic, forming tabular or fibrous aggregates. The composition is commonly described as calcium- and aluminum-rich silicate with trace magnesium and fluorine. Its theoretical density ranges from 3.2 to 3.4 g/cm3. Stillingum is said to occur in hydrothermal environments and in low-grade metamorphic rocks, often in association with quartz, fluorite, and calcite.

Etymology: The name honors mineralogist Sven Stilling and uses the conventional -um suffix for minerals. Type locality: the fictional Stilling Mine, Norway.

Occurrence: In teaching materials, stillingum is proposed to be rare, with limited synthetic production in demonstrations of crystal growth and phase relations.

Gemology and applications: In speculative fiction and pedagogy, it is occasionally described as a gemstone substitute due to its high refractive index, though there is no real-world synthesis or market.

See also: List of minerals; Mineralogy; Crystal chemistry.