rare earth elements
Monazite. Credit: E. Offermann. Coll. A. Kandblauer, SVSMF.
Rare earth elements are a group of metallic elements having closely similar chemical properties. They are mainly trivalent, but otherwise similar to the alkaline earth elements. The group consists of the lanthanide elements with atomic numbers 57 (lanthanum) to 71 (lutetium), plus scandium (21) and yttrium (39).