Recent Examples on the WebThe least abundant of these, thulium (Tm) and lutetium (Lu) are 200 times more abundant than gold. Willy Shih, Forbes, 24 Feb. 2021 The 794 nm photon interacts with a lithium-niobate crystal doped with thulium, so that the photon’s state becomes stored in the crystal. Anil Ananthaswamy, Scientific American, 19 June 2019 Electronic shielding by closed shells in thulium compounds. Spencer Reiss, WIRED, 1 May 2004