A rare metallic element of the boron-aluminium group, found in gadolinite and other rare minerals, and extracted as a dark gray powder. Symbol Y
. Atomic number 39. Atomic weight, 88.9. [1913 Webster
" Associated with yttrium are certain rare elements, as erbium, ytterbium, samarium, etc., which are separated in a pure state with great difficulty. They are studied by means of their spark or phosphorescent spectra. Yttrium is now regarded as probably not a simple element, but as a mixture of several substances."