This carries high grades of neodymium, praseodymium, lanthanum, and cerium with a small amount of heavy rare earths in the deposit.
www.proactiveinvestors.com.au While these compounds do exist, analogous chemicals that contain lanthanum, praseodymium, gadolinium, holmium, terbium, or ytterbium have not been discovered, as of 2008.
en.wikipedia.org Due to high cost to extract the other lanthanides a mischmetal with more than 50% of lanthanum is used instead of pure lanthanum.
en.wikipedia.org Three group 3 elements occur naturally, scandium, yttrium, and either lanthanum or lutetium.
en.wikipedia.org The principal use of lanthanum hexaboride is in hot cathodes, either as a single crystal or as a coating deposited by physical vapor deposition.
en.wikipedia.org