LIBS Sorting

LIBS presently is mainly used for quantitative and semi-quantitative analyses. Much less attention has been paid to the potential of LIBS for qualitative analysis, which may be effectively used in radiometric sorting of minerals. In this sense we do not need to determine a detailed chemical composition of the minerals, but rather the aim is to find the specific lines, which enable us to identify the corresponding mineral. LIBS mineral sorting is in its early stages, but the prospects are very good. We developed the corresponding database of time-resolved LIBS under 1,064, 532, 355 and 266 nm laser excitations for the spectral range from 200 to 900 nm. 

The data from Table 8.2 evidence that practically in all cases it is possible to find the emission lines, which enable us to differentiate between accepted and rejected elements. Based on the minerals LIBS library, a method 

Range ofXRF spectrum Element Interfering element I II III 

It is evident that LIBS sorting may not be accomplished by integral irradiation, because it is based upon plasma analyses generated on relatively small area by focused laser beam. Nevertheless, if each pebble is composed of only one mineral, one laser pulse will be representative enough in order to determine the pebble composition. For uniformly embedded ores the situation is different and 2-5% of the pebble area has to be covered for the confident identification of useful mineral. Non-uniformly disseminated ores demand even more detailed scanning, which has to be determined individually for 

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It is possible to suppose that LIBS sorting may be better than the luminescent one. It is clearly seen that the corresponding spectra of borosilicates, quartz and calcite are totally different (Fig. 8.4), which make radiometric sorting easy and confident. 

About 90% of manganese ore is used in steel smelting. Although there are more than 300 manganiferous minerals, the common ore minerals are largely mixtures of manganese oxides and hydrated oxides. The usual field terms are psilomelane for a hard massive mixture of oxide minerals, pyrolusite for a soft black earthy mixture, and wad for impure, brown earthy oxides and hydrated oxides. LIBS sorting may be effective in this case (Fig. 8.11). 

Prototype LIBS sorting system is firstly developed by International Technologies Lasers (ITL) Company. In present modification, the system accomplishes evaluation of conveyed rocks composition. Beta site test was successfully accomplished at 2004 on Four Corners Mine, Florida. 

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