Chemical and mineral composition of ores of the Buruktal deposit (Orenburg Region): Type of the nickel-bearing weathering crust

The Buruktal nickel and cobalt deposit, the largest in Russia, is located in the Orenburg Region and is confined to the weathering crust of the ultramafic massif of the same name in the southern portion of the Buruktal synclinorium. Nickel and cobalt in ores of the deposit are predominantly concentrated in serpentine and montmorillonite group minerals, as well as in magnetite, goethite, hematite, and chlorite. The average nickel grade is 0.86 % and that of cobalt is 0.09 %. The composition of the Buruktal ores was compared with ores of nickel-bearing weathering crusts in other countries. The data obtained were used to determine the weathering crust profile type in accordance with the international classification. Because of the high nontronite content (up to 13 %), relatively low iron oxide and hydroxide content (12 %), along with the higher serpentine content (27 %), the Buruktal deposit cannot be classified neither as a silicate weathering crust, nor as clayey one. Therefore, it is classified as a mixed, clayey-silicate type, which stronly complicates selection of the beneficiation technology.