Xilyymi

Xilyymi is a fictional mineral used in science fiction and worldbuilding. It is described as a rare silicate mineral with luminescent properties that forms under extreme metamorphic conditions in a hypothetical planetary crust.

In the fictional canon, xilyymi crystallizes in hexagonal prisms, is translucent, and shows a pale teal to blue-green color. It is said to be photoluminescent, emitting a soft glow when exposed to ultraviolet light. Reported hardness is around 6.5 on the Mohs scale, with a refractive index near 1.62.

Etymology and use: The name combines a constructed root xil- with the suffix -ymi, drawn from the language of the Xilians in the stories. Within narratives, xilyymi is prized as an energy storage material and as a durable optical component for sensors and lasers.

In real-world geology, there is no confirmed mineral named xilyymi; the concept exists solely in fictional settings.