Gold in pyrites and sulfides by scintillation analysis

The method of scintillation atomic emission spectrometry (SAES) allows determination of the form of the element present in the sample and the size of inclusions in addition to the total content of the element in the direct analysis of powder samples. The aim of the work is to verify the expedience of using the direct method of analysis of individual gold particles in studying the possible forms of gold appearance in pyrites and sulfides, including the so-called «invisible» finely divided gold. The measurements were carried out both on individual pyrite single crystals, and on the samples of sulfide gold and brown coal deposits of Kazakhstan. The studies were carried out on a Grand-Potok complex (VMK Optoelektronika, Ltd.) equipped with a laser ablation system and a system for injection of aqueous solutions and aerosols samples. The samples of pyrite crystals of various sizes were analyzed to determine the content and speciation of gold in the samples. No dependence of the gold content on the crystal size was noted for all the studied pyrites. It is shown that gold and other precious metals are concentrated in the surface layers of pyrite crystals and in crystal lattice defects in the bulk of the crystal (according to SAES data during laser ablation of the sample in an arc discharge). The total content of gold in the bulk of pyrite crystals is about 2 g/ton, platinum and silver is less than 0.02 g/ton, while the content of Au, Ag, Pt on the surface ranges from 2 to 5 g/ton. The detection limit of gold determination by the SAES method is 0.01 g/ton. The SAES method can be used for determination of the gold speciation in pyrites and sulfides (finely dispersed, individual particles up to 1 μm or even less).

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