Liberation of Tl-Rich Minerals From the Ore of the Allchar Mine

Abstract

The methods are described of selective separation of thallium mineral lorandite from the Allchar hydrothermal-volcanogenic Sb-As-Tl deposit (FYR Macedonia) characterized by relatively complex mineralization. In addition to antimony and arsenic, the Allchar Mine at the village of Majden works one of the richest thallium mineral lorandite deposits. The aim of the research was to separate lorandite as much and as free grain as possible mainly through physical concentration. Thallium is very important because of a possibility to apply its mineral lorandite (TlAsS2) in obtaining knowledge in fundamental investigations. The reaction between Tl and solar neutrinos, producing Pb, is on the purpose of studing the neutrino flux from the Sun. For this purpose, a thallium-rich mineral is required as the target. Geochemically natural, pure thallium mineral lorandite is used to test solar neutrino under the current, two decades long LOREX Project. The Allchar ore from Crveni Dol contains a comparatively complex association of Sb-As-Tl minerals: pyrite, marcasite, antimonite, arsenopyrite, realgar, auripigmentum, barite, cinnabar, and accessory thallium lorandite, vrbaite, raguinite, picopaulite, parapierrotite, rebulite, greigite, tetrahedrite, and various sulphosalts that are found only in Allchar. The research used conventional laboratory methods for mineral fractionation and for liberation of lorandite grains, which included size reduction, sieve analysis, Wilfley table, sink and float analysis (bromoform, methylene iodide), electrostatic separation, electromagnetic separation and centrifugal separator. Gradual separation from successive communition and classification of fractions allowed separation of the free sink (heavy) product from which nonconductive minerals, including lorandite, were selected.