Geology Reference
In-Depth Information
800
4.0E-03
Exergy cost
Ore grade
700
3.5E-03
600
3.0E-03
500
2.5E-03
400
2.0E-03
300
1.5E-03
200
1.0E-03
100
5.0E-04
0
0.0E+00
Year
Fig. 13.9 Ore grade and exergy replacement cost of Australian silver mines
(Geoscience, 2005). Hence, why production patterns may not follow those typical
for other commodities.
13.3.5 Lead
Lead production has followed a generally increasing trend since the beginning of
its mining industry. Lead is closely allied to silver in terms of mining, through
lead-zinc-silver ores. In Australia, almost all lead is mined this way, with only
minor quantities being produced from lead only ores. The polymetallic lead-zinc-
silver-copper-gold ores found at Rosebery in Tasmania have been a moderate but
important source of lead since the 1930s. Prior to the discovery of the large Broken
Hill field in New South Wales, the Northampton lead field in Western Australia was
a very minor producer and although the grades appeared very rich at 50-60%, this
was most likely an artifact of selective hand-picking of ore. Other lead producers in
Australia include Mt Isa and CanninGt mines in Queensland, the Elura/Enterprise
mine in New South Wales and the McArthur River Mine in the Northern Territory 5 .
As in the case of silver, lead ore grades decreased dramatically over a short period
of time. During the first 20 years of the lead industry, ore grades remained at
around 60% albeit from that point on they dropped to below 20%. In fact, the 2007
ore grade is as low as 3.6%. Accordingly, the natural bonus of 1.2 toe/t in 1877
decreased to 0.8 toe/t in 2007 (see Fig. 13.11).
5 Historic mines or producers include Captain's Flat, Woodlawn, Hellyer, Magellan and Century
Zinc.
 
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