con ▁and ▁il men ite . ▁Mon az ite ▁can ▁be ▁isolated ▁as ▁a ▁nearly ▁pure ▁concent rate ▁by ▁the ▁use ▁of ▁gravity , ▁magnetic , ▁and ▁electro static ▁separation . ▁ ▁Mon az ite ▁sand ▁depos its ▁are ▁in ev it ably ▁of ▁the ▁mon az ite -( C e ) ▁composition . ▁Typ ically , ▁the ▁l anth an ides ▁in ▁such ▁mon az ites ▁contain ▁about ▁ 4 5 – 4 8 % ▁cer ium , ▁about ▁ 2 4 % ▁l anth an um , ▁about ▁ 1 7 % ▁ne od ym ium , ▁about ▁ 5 % ▁pr ase od ym ium , ▁and ▁minor ▁quantities ▁of ▁sam arium , ▁g ad olin ium , ▁and ▁y tt rium . ▁Europ ium ▁concentr ations ▁tend ▁to ▁be ▁low , ▁about ▁ 0 . 0 5 %. ▁South ▁African ▁" rock " ▁mon az ite , ▁from ▁Ste enk amps k ra al , ▁was ▁processed ▁in ▁the ▁ 1 9 5 0 s ▁and ▁early ▁ 1 9 6 0 s ▁by ▁the ▁L inds ay ▁Chem ical ▁Division ▁of ▁American ▁Pot ash ▁and ▁Chem ical ▁Corporation , ▁at ▁the ▁time ▁the ▁largest ▁producer ▁of ▁l anth an ides ▁in ▁the ▁world . ▁Ste enk amps k ra al ▁mon az ite ▁provided ▁a ▁supply ▁of ▁the ▁complete ▁set ▁of ▁l anth an ides . ▁Very ▁low ▁concentr ations ▁of ▁the ▁heav iest ▁l anth an ides ▁in ▁mon az ite ▁just ified ▁the ▁term ▁" rare