Application of thermal treatment for the interpretation of photoluminescent centres in minerals

The influence of thermal treatments on photoluminescence spectra of several minerals has been investigated. By applying step-wise heating, new luminescence centres were detected which had been not previously recognized in the corresponding minerals. Luminsecence centres appearing as result of valence changing during oxidizing heating include: (i) (UO₂)²⁺ as a result of nonluminescent U⁶⁺ transformation in zircon, barite, francolite and chert; (ii) Eu²⁺ as a result of nonluminescent Eu⁺ transformation in barite. Luminescence centres which were most stable under thermal treatment were Fe³⁺ in zircon and Mn²⁺ in barite. Luminescence centres with similar spectral-kinetic properties but with different thermal stability which allowed them to be separated and properly identified were different metaloxygen complexes (MeO_n)^m- in zircon.