Cassiterite luminescence

At the third level, the most detailed partition of luminescence minerals is carried out on the basis of metals in the mineral formulae, hi rare cases we have minerals with host luminescence, such as uranyl minerals, Mn minerals, scheelite, powellite, cassiterite and chlorargyrite. Much more often luminescent elements are present as impurities substituting intrinsic cations if their radii and charges are close enough. Thus, for example, Mn + substitutes for Ca and Mg in many calcium and magnesium minerals, REE + and REE substitutes for Ca, Cr substitutes for AP+ in oxygen octahedra, Ee substitutes for Si in tetrahedra and so on. Luminescence centers presently known in solid-state spectroscopy are summarized in Table 4.2 and their potential substitutions in positions of intrinsic cations in minerals in Table 4.3. 

The considerable zonation was found in CL of cassiterite with respect to W and Ti. It was concluded that W is responsible for blue luminescence. 

Fig. 4.27. Laser-induced time-resolved luminescence spectra of cassiterite demonstrating intrinsic, possibly Sn " centers...

Gaft M, PanczCT G (2013) Lasta- induced time resolved luminescence spectroscopy of minerals - a powerful tool for stedying the nature of emission centers. Miner Petrol 107 363-372 Gaft M, Vorontsova L (1982) Luminescence of cassiterite and the possibilities of its practical use. Miner J4(5) 75-78... 

In order to find impurity responsible for yeUow emission, artificial Sn02 have been studied activated by different impurities such as Ti, Nb, Ta, W, Fe (Gaft et al. 1982). From crystallochemical positions such ions are capable to substitute for Sn" " ". Nevertheless, the correlation of luminescence with any impurity was not found. From the other hand, in nominally pure super pure Sn02 all luminescence bands have been found, which were detected in natural cassiterite (Fig. 5.90). Thus it was concluded that luminescence is connected to intrinsic, namely to Sn of diverse valence, possibly Sn. Blasser et al. (1981) arrived at the same conclusion about intrinsic nature of Sn02 luminescence. 

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