australia's identified mineral resources 2005 - Geoscience Australia

AUSTRALIA’S IDENTIFIED MINERAL RESOURCES 2005
Bauxite
Bauxite is a heterogeneous naturally occurring material from which alumina (Al 2 O 3 ) and aluminium
are produced. The principal minerals in bauxite are gibbsite (Al 2 O 3 .3H 2 O), boehmite (Al 2 O 3 .H 2 O)
and diaspore, which has the same composition as boehmite but is denser and harder.
Over 85% of the bauxite mined globally is converted to alumina for the production of aluminium
metal, an additional 10% goes to nonmetal uses in various forms of specialty alumina, and the
remainder is for nonmetallurgical bauxite applications. In nearly all commercial operations, alumina
is extracted (refined) from bauxite by a wet chemical caustic leach process known as the Bayer
process. Alumina is smelted using the Hall-Heroult process to produce aluminium metal by
electrolytic reduction in a molten bath of natural or synthetic cryolite (NaAlF 6 ).
Australia’s aluminium industry is a large integrated sector of mining, refining, smelting and semifabrication,
which is of major economic importance nationally and globally. The total value of all
sector exports was over $7.8 billion in 2004. The industry consists of five bauxite mines, seven
alumina refineries, six primary aluminium smelters, twelve extrusion mills and two rolled product
(sheet, plate and foil) mills. It directly employs over 16 000 people (indirectly many more) and is
particularly important in regions such as North Queensland, the Hunter Valley, Southwest Victoria,
Southwest Western Australia, the Northern Territory and North Tasmania.
Resources
Vast resources of bauxite, located in the Weipa and Gove regions adjacent to the Gulf of Carpentaria
and in the Darling Ranges south of Perth, underpin the long-term future of Australia’s aluminium
industry. Deposits in these regions rank among the world’s largest identified resources in terms of
extractable alumina content. Bauxite deposits at Mitchell Plateau and Cape Bougainville in the north of
Western Australia are uneconomic to develop but are a significant potentially viable future resource.
EDR of 5.7 Gt in 2004 represented an increase of over 3% compared to the previous year. As with
the previous year, the increase resulted from a net effect of new drilling, changes in cut-off grades,
mining depletion and reclassification of resources. Subeconomic demonstrated resources decreased
by just under 0.1 Gt following upgrading of some resources to EDR in Queensland. Expansion of the
Weipa bauxite mine resulted in a significant increase in production from the mining and processing
of lower grade ores. Inferred resources increased by over 80% to 1.1 Gt due to reclassification of
resources by companies when aligning with JORC standards, principally in Western Australia.
Accessible EDR
Less than 10% of bauxite EDR is inaccessible for mining. This involves small areas of the Darling
range (WA) within mining leases, where for environmental reasons bauxite is not available for
extraction. The ratio of AEDR to current mine production shows the resource life for existing
bauxite operations is on average around 70 to 80 years. The potential of unexplored regions,
however, is likely to extend resource life well beyond this.
JORC Reserves
Approximately 35% of AEDR comprises JORC Code reserves. The remaining represents resources
assessed by Geoscience Australia as being economically recoverable from industry’s measured and
indicated categories of mineral resources, as defined under the Code and other classification systems
used by non-listed ASX companies.
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Exploration
Data relating to exploration for bauxite specifically are not available nationally.