Lanthanum

Description: Lanthanum is a silvery-white metal that is malleable, ductile, and soft enough to cut with a knife. It is one of the most reactive of the rare-earth metals. When exposed to air, it oxidizes quickly. Lanthanum is attacked slowly by cold water, but rapidly by hot water.

Source: Lanthanum can be found in rare-earth minerals like cerite, monazite, allanite, and bastnasite. Lanthanum is found in significant amounts in the ores monazite and bastnasite, with concentrations of up to 25% and 38% respectively. Misch metal, which is used to make lighter flints, contains about 25% lanthanum.
Lanthanum and other rare earths have become much more widely available in recent years. The metal is produced by reducing anhydrous fluoride with calcium.