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From The Collaborative International Dictionary of English v.0.48:
Neodymium \Ne`o*dym"i*um\, n. [NL. Dee Neo-, and Didymium.] (Chem.) The chemical element of atomic number 60, one of the rare earth elements. Symbol Nd. Atomic weight 144.27. Note: It is a rare metallic element occurring in combination with cerium, lanthanum, and other rare metals, and forming amethyst-colored salts. It was originally thought to be part of a supposed new element didymium, obtained from cerite in 1843. Later this was resolved into two elements, neodymium and praesodymium by von Welsbach in 1885. It is chiefly trivalent. It is a faintly yellow metal. [1913 Webster +PJC]