Kainosite is a silicate mineral that has the formula of Ca2(Y,Ce) SiO4O12(CO3)•(H2O). Kainosite was first discovered in Norway and was named by Adolf Erik Nordenskiöld (1832–1901) in allusion to the Greek word for "unusual" for its rarity and exotic composition.
Kainosite, is part of the orthorhombic crystal class minerals, which is a system that results from stretching a cubic lattice along two of its orthogonal pairs. Kainosite is a biaxial mineral, so the light entering its crystals will be polarized in two vibration directions (XYZ) for it has two optic axes. Because Kainosite is orthorhombic, the vibration directions XYZ coincide with the a,b,c crystallography axes.
Kainosite is very rare and mostly found in Russia in vugs , pegmatites, and alkalic complex as an altered product of the mineral kuliokite.