Lanthanum, chemical element, symbol La; for physical constants see Periodic Table. Lanthanum was discovered by Carl Mosander in 1839. It occurs in the minerals cerite, bastnasite, and monazite which is the principal source of the element. The metal is prepared by reducing the anhydrous fluoride with calcium. Lanthanum is silvery-white, malleable, ductile, and soft enough to be cut with a knife. Ion-exchange and solvent extraction techniques have led to much easier isolation of the so-called “rare-earth” elements. Lanthanum and its compounds are used in carbon lighting applications, special glasses, hydrogen sponge alloys, and misch metal.