Lithoids are "a bigger and boulder species type made entirely of sapient rock who eat minerals for sustenance, are long-lived, and can colonize in almost any environment" (from Stellaris DLC listing

Lithoids are a sentient rock aliens from Stellaris, a 4x strategy game set in space. Their designs center around being made of stone in one way or another. They can be anything from a floating pile of rocks with hands, to a stack of boulders held together by trees, to the more popular one on this site- a lizard made of stone. Like many of stellaris' portrait designs the requirements are not set in stone.