lyyn

Lyyyn is a fictional mineral featured in speculative fiction and worldbuilding. Described as a luminescent aluminosilicate, it is said to form in hydrothermal veins within basaltic hosts and is valued for its vivid blue-green glow.

Properties typically attributed to lyyyn include a composition of calcium and aluminum silicate with trace dopants of europium and terbium, which produce its characteristic emission. It is described as having a Mohs hardness of 6–7, a refractive index around 1.62–1.70, and distinct cleavage along two directions. When exposed to ultraviolet light, lyyyn reportedly glows with a persistent blue-green emission, with the luminescence fading slowly in darkness.

Occurrence is described in fictional settings such as the planet Veridia and analogous world-building contexts. Lyyyn is said to form through gradual crystallization of silica-rich fluids in hydrothermal systems and is often found in association with quartz, spodumene, and zeolites in cavernous environments.

Uses within stories typically include decorative applications and photonic functionality, where the mineral serves as a light-guiding material or as luminous signage. In some cultures within the fiction, lyyyn artifacts are valued for ritual or ceremonial purposes and as a source of inspiration for designers of optical devices.

Etymology and nomenclature in fiction suggest the name derives from a constructed language spoken by mining colonies, with "ly" meaning light and "yn" denoting stone. In published materials, the term may appear with minor spelling variants.