 Ytterbium is found with other rare earth elements in several rare minerals . It is most often recovered commercially from monazite sand ( 0 @.@ 03 % ytterbium ) . The element is also found in euxenite and xenotime . The main mining areas are China , the United States , Brazil , India , Sri Lanka , and Australia ; and reserves of ytterbium are estimated as one million tonnes . Ytterbium is normally difficult to separate from other rare earths , but ion @-@ exchange and solvent extraction techniques developed in the mid- to late 20th century have simplified separation . Known compounds of ytterbium are rare and have not yet been well characterized . The abundance of ytterbium in the Earth 's crust is about 3 mg / kg . 
