The Isa Mine of Mount Isa Mines Limited produces 2.6 million tonnes of silver-lead-zinc ore annually from sub level open stopes of which approximately 40% comes from the narrow Racecourse orebodies below 15 level._x000D_
Geologically the stoping environment is complicated by highly fissile shale hangingwalls and below 17 level by a high stress regime._x000D_
The realization that major hangingwall failures and generally poor ground conditions could lead to serious dilution problems, and ultimately production shortfalls, prompted investigations into the use of low strength explosives.