The effects of UV radiation on the thermoluminescence (TL) properties of natural materials, in contrast to synthetic materials, have been scarcely studied. We report on the UV-induced thermoluminescence emission of a Turkish ulexite (NaCaB5O6(OH)(6)center dot 5H(2)O) that displays very complex TL glow curves, with at least three groups of components peaked at 130-140 degrees C, 240 degrees C and, 340 degrees C, wherein the last group is weaker. Such emission could be associated with structural changes in the lattice as well as alkali self-diffusion processes. The UV exposure performed at controlled temperatures (at room temperature (RT), 50 degrees C and 100 degrees C) produced a (i) different evolutions of the intensities of each maximum, which are directly related to the controlled thermal treatment; (ii) different intensity ratios among the groups of components; (iii) different activation energies (E-a) (1.13 eV for RT, 0.99 eV for 50 degrees C and 0.49 eV for 100 degrees C) calculated using the initial rise method; and (iv) similar scattering values (12.4%, 8.2% and 12.8%), which were not a function of the controlled temperature. The thermal stability tests conducted on this borate at different temperatures, based on the T-stop protocol, confirm the presence of a continuum in the distribution of the trap system with progressively increasing E-a (from 0.60 to 0.90 eV). (C) 2015 Elsevier B.V. All rights reserved.