Luminescence Sorting

Diamond luminescence was studied mainly with the two following aims to carry out a fundamental investigation of its physical properties and to determine the optimal conditions for luminescent sorting of diamond bearing rocks. For the first task, diamond photoluminescence was studied at liquid nitrogen temperature at which luminescence centers are marked by characteristic zero-phonon fines and are much more informative then at room temperature. For the second task, were diamond is one of the first minerals for which luminescence sorting was used, liuninescence properties should be studied at 300 K. In the first stages it was established that X-ray luminescence of the A-band 

At the present time new deposits have been discovered which contain diamonds without luminescence under X-ray excitation. Sometimes the portion, which is unrecoverable in X-ray luminescent sorters, is big enough to warrant the development of a new sorting method. The luminescence spectra were investigated under excimer (193,222,248 and 308 nm), nitrogen (337 nm) and dye laser (340-360 nm) excitations (Fig. 8.2). 

---

Fluorite is used as a flux in steel making and in the smelting of ores. Luminescence sorting of fluorite is a well-known technique, which is based on the strong blue luminescence of Eu. ... 

These minerals have never been mentioned as potential targets for luminescent sorting because of the absence of natural emission even under laser excitation. LIBS may be an excellent opportunity, because all those elements have strong and characteristic lines. Figure 8.17 present examples of malachite (Cu), galena (Pb), and sphalerite (Zn) breakdown spectra. 

Table 8.4 Results of datolite CaB(Si04)(OH) ore laser luminescent sorting...

---