Au
Production
Gold production has begun from the
newly-stacked heaps at Lluvia de Oro.
Leaching in Pads SW1 & SW2 is resulting in the gold extraction
which was predicted, and is expected to yield a little over 1000 oz.
Au by June 30. Four new heaps are being stacked in coming months, so
that total gold production by year-end 2011 should exceed 12,000
ounces Au.
Gold Pours
The ADR Plant and Refinery at Lluvia de Oro are recovering gold as expected.
The planned expansion of heap leach capacity during the remainder of
2011 will result in a requirement for expanded gold recovery
circuits. Expansions to each unit in the gold recovery circuit have
been designed and budgeted, and are in the early stages of equipment
procurement and construction.
Mine Preparation
During late 2010 and early 2011, major
pre-stripping of ore reserves was accomplished at Lluvia
de Oro. This work has allowed the concurrent development of multiple
ore mining zones. As a result, ore stacking on new heaps is planned
at over 250,000 tonnes per month from now
until end of 2012.
Ore mined at Lluvia
de Oro is being segregated into 4 grade ranges for optimal
processing.
These grade ranges are:
High Grade HG
1.00 g/tonne Au, and higher
Mid Grade
MG
0.35 � 0.99 g/tonne Au
Low Grade
LG 0.20 � 0.35
Sub Grade
SG 0.10 � 0.19
Heap Leach
Pad Preparation
Four cells on Pads SW1 & SW2 are now
under leach and delivering pregnant solution to the ADR Plant. Two
more cells will be loaded with ore from the Creston Pit during May
and June. Pads SW1 & SW2 will have a total of 800,000 tonnes of Mid Grade MG ore under leach by August.
Pads 7, 8 & 9 are being prepared for new
ore delivery which is expected to commence in July. Leaching on Pads
7, 8 & 9 will commence in August. These Pads will have 400,000 tonnes of Mid Grade MG ore under leach by
November.
Construction is underway on the new Lluvia Dos Pad, which will have capacity for all Lluvia ore reserves currently known (design
capacity is 45 million tonnes). Two special
lanes on this pad will be stacked to just 3 meters depth with High
Grade (HG) ore (grades averaging 1.5 g/tonne
Au). Crushing and Conveyor Stacking of HG ore will begin in late
July, and leaching will begin in August.
One lane of the Lluvia
Dos Pad will begin receiving Mid Grade (MG) ore in September. The MG
ore will be stacked to a height of 10 meters. A new lane for MG ore
will be constructed every 4 months to match mine production output.
A large Pad for Low Grade (LG) ore will be
completed by October. The tonnage of LG ore is significant at Lluvia, and a lower cost pad is planned for
processing it, by Dump Leaching. The Dump Leach Pad will hold 4
million tonnes of LG ore and will be
stacked to a height of 35 meters.
Ounces
Forecast
All Lluvia ore in
the HG and MG classifications are part of the NI 43-101 compliant
reserves reported in July 2010. The NI 43-101 reserves include all
ore stacked on Pad SW1 & SW2, Pads 7, 8 & 9, Pad HG and Pad
MG. These Pads are forecast to be stacked with 2 million tonnes of HG and MG ore during 2011.
If this Pad loading rate is achieved, the HG
and MG ore stacked will contain 43,000 ounces Au, all part of the
published NI 43-101 reserves. Based on the leaching recovery rate
projected in the NI 43-101 technical report of July 2010, over 10,000
ounces Au are forecast to be leached and recovered by year-end 2011.
Production Plans for 2011 � 2012 forecast
more than 5 million tonnes of ore will be
stacked and leaching by end of 2012, all from the published NI 43-101
reserves for Lluvia de Oro. These ore tonnes will contain a total of approximately
100,000 ounces of gold. Gold recovered and produced is thus forecast
to be over 50,000 ounces by end of 2012.
Copper
Control
Copper control at Lluvia
de Oro and La Jojoba will be achieved by three methods (A, B &
C), each independent and operating in sequence.
A. The first method is segregation of leach
solutions by gold and copper content, so that each metal can be
removed and recovered by distinct processes. Blending of gold-rich
and copper-rich solutions will be avoided by the leach pad design and
leaching sequence.
B. The second method is aggressive removal
of copper within the gold plant, by addition of a series of extra
process operations targeting the copper. These extra operations occur
in carbon adsorption, acid washing of carbon, cold stripping,
electro-winning, sludge processing and refining.
C. The third method is a novel process
called ASPN. This stands for Acidification, Sulfidation,
Precipitation, Neutralization. It differs
significantly from its cousin, the SART process. It has two important
features. The first feature is the relative simplicity of the
process, which leads to lower capital costs. The second feature is
the planned close proximity to the heaps producing the copper-rich
solutions, which leads to lower operating costs.
Currently at Lluvia
de Oro methods A and B are in use and operating. These two methods
are sufficient for Lluvia ores because they
are relatively low in copper content. Method C (ASPN) will be applied
to Jojoba ores, which have a copper content 4 times greater than
those of Lluvia ores.
Method C (ASPN) is currently being tested on
site at Lluvia. Copper precipitation from
the gold-rich solutions has been demonstrated. The ASPN process will
soon be operating as a continuous-flow pilot-scale test, processing
bleed streams from different heaps with varying ore characteristics.
During the pilot-scale testing phase, method A allows copper-rich
solutions to be segregated for testwork and
optimization of the ASPN process.
The full-scale application of the ASPN
process is expected to be constructed and operating at least a year
before Jojoba ores are being mined and leached.
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