Cerium
Cerium, the most important of the rare earth elements, is obtained from monazite (phosphates of rare earth metals) or from thorite (silicates of rare earth metals) after removal of thorium. Cerium is produced by metallic thermal reduction of halides using calcium or lithium as reducing agents, or by electrolysis of molten chloride. It is a gray malleable metal, slightly harder than lead, which produces sparks when rubbed against a rough surface
Source: "Explanations to the Combined Nomenclature of Goods for Foreign Economic Activity of the Russian Federation (HS Code of the Russian Federation)" (prepared by the Russian Federal Customs Service) (volume 1, sections I-VI, groups 1-29