On the mining side, where production is currently some 15,000 t/d of copper ore and 12,000 t/d of lead ore (both from underground), the development of techniques has been impressive and continuous, as related under 'Copper'. The extraction of these large tonnages, portion of which is from relatively narrow orebodies, demands extraordinary measures in planning and control of sloping practices and support and filling of openings, together with drilling and firing techniques; many innovative practices have been devised accordingly.

he metallurgical techniques and operating skills developed at Mount Isa will be tested to the limit in determining the future of the Mount Isa group's McArthur River zinc-lead prospect in the Northern Territory, where the texture of the ore is even more complex than in the Mount Isa orebodies, with very finely disseminated zinc and lead sulphides interwoven with pyrite and silica to a degree which puts the ore outside the scope of flotation alone. Some combination of pressure leaching and flotation is indicated as the most likely treatment; at this stage further development of the prospect is uncertain. Nevertheless the orebody of some 220 Mt carrying 9 per cent Zn, 4 per cent Pb and 40 g/t Ag is one of the largest known undeveloped zinc-lead sources in the world and presents a formidable challenge to the metallurgists and chemical engineers.

Australian Academy of Technological Sciences and Engineering