Xstrata Zinc’s Black Star open-pit mine in Mount Isa, Queensland, is part of Xstrata’s Mount Isa Mines (MIM) operations. Mining began at the Black Star pit in early 2005 and had yielded 1.4 million tonnes by the year’s end. Initial mining was based on 25Mt of reserves, with mining occurring at a rate of 2.3 million tonnes per annum.
In 2010 Xstrata Zinc proposed to expand its Black Star operations in order to extend the life of the mine at current production rates through to 2016.
In 2005 the combined MIM mines delivered 4.78Mt of ore, of which 4.4Mt were treated, yielding 231,000t of zinc in concentrates, 160,000t of lead-in-bullion and 11.36 million ounces of silver in crude lead. The current MIM lead mine concentrator was built in 1966 and included rod and ball milling, lead-silver flotation, zinc flotation and low-grade middling’s recovery. In 1982 MIM added heavy-medium separation to pre-concentrate the mill feed. Later enhancements have included column cell flotation. Plant capacity was increased to 2.5Mtpa in mid 2000. A blast furnace converts sintered lead-silver concentrate to lead-silver bullion for subsequent refining at the Northfleet refinery in the UK. Zinc concentrates are currently exported and low-grade middling concentrates go mainly to Imperial smelting process plants.