The treatment plant at Martha Mine was
upgraded from a nominal throughput of 110tph (O.93mtpa) to 150tph (1.25mtpa)
late 1999. Post-upgrade performance did not meet expectations when treating
either the competent primary ore or the clay-rich oxide ore.

Plant throughput is constrained by milling
capacity when treating the competent primary ore. This is not an issue at
present as current plant feed is oxide ore from the top of the open-pit, but
will become so in future years as the pit deepens. To counter this future
threat, ball mill power has been restored to 1100kW through modifications to the
drive train. The addition of a crushing circuit may also be
necessary.

Plant throughput was originally constrained
by thickener and leach/adsorption tank issues when treating the oxide are.
Changes to plant equipment and operations has seen the removal of these
constraints and throughput on this material is no longer a problem.

The most significant issue facing plant staff
at present is the high silver grade and its impact on gold recovery. These high
grades impact upon recovery through losses caused by insufficient leach and
adsorption capacity. To counter this, the geology, mining, and milling teams are
working together to blend the high grade silver zones with lower grade ores -
this is seen to be the quickest and most cost effective way to deal with the
issue. The plant design has also been evaluated with a view to modifying it to
cope with the higher silver grades. The viability of these modifications will
depend on cost and time (that is, the length of time to implement any
modifications versus the length of time to mine out the high silver
zones).