Characterization and Pre-concentration of Low Grade PGE Ores of Boula Area, Odisha using Gravity Concentration Methods

Platinum group elements (PGEs) are scarce in nature and have very limited deposits of economic importance world over. The deposits have very low tenor and require pre-concentration to recover the PGE values. Compared to world occurrences, only a few occurrences have been so far reported in India. Out of them, Boula-Nuasahi occurrence is one where PGE mineralization is confined to a narrow breccia zone and the grade is very low (< 2 ppm). Ferrochromite and Base metal sulfides are two important hosts for this mineralization. Chalcopyrite and pyrrhotite are the main sulfide minerals present in this sample. Tremolite is the major silicate mineral followed by chlorite, enstatite and riebeckite. Chromite is the only primary oxide mineral present. Sudburyite and sperrylite are major PGE minerals. Other PGE minerals such as braggite, laurite, michenerite and testibiopalladite are also present. The PGE minerals exhibit associations with ferrochromite, sulfide and silicate. The minerals are of very fine size with the average size less than 20 micron. Very low grade and complex mineralogical attributes coupled with very fine size, make processing of this scarce resource very necessary and important. An attempt has been made to pre-concentrate the PGE values using different gravity separation techniques. A laboratory model KC-MD3 Knelson concentrator performed better compared to the others. The operating variables such as; G-force and fluidization pressure are varied to maximize the recovery and grade.