The Lady Loretta silver-lead-zinc deposit lies north of Mount Isa in folded and faulted Proterozoic carbonate sediments._x000D_
The deposit was discovered in the late 1960's as a result of a soil geochemical survey. Subsequent surface drilling outlined mineralisation folded into a synclinal structure extending to a depth of 460 m and containing exceptionally high grades within the keel of the syncline._x000D_
Pancontinental Mining Limited and Outokumpu Oy of Finland acquired the property in 1985._x000D_
Due to limitations of the previous surface drilling in accurately determining the complex structures and orebody limits, it was decided to carry out an underground exploration programme prior to a feasibility study. A shaft sinking, underground development and underground diamond drilling contract was let for a 470 m deep, 4.8 m diameter shaft, 10 000 m of diamond drilling, and the taking of a bulk sample._x000D_
This paper discusses the technical aspects of the programme, detailing the processes followed in the selection of shaft location, size and layout, the methods adopted for shaft sinking and level development and the gathering of geological, geotechnical, hydrological and metallurgical data from the underground development, sampling and exploration drilling._x000D_
Results gained from the exploration programme have vindicated the decision to proceed underground before a feasibility study was finalised. Major changes have been indicated in the structure of the orebody and the ore distribution and significant geotechnical advances have resulted from underground data collection which will have positive effects on development design.