Avocet Mining PLC Prospectus December 2011

Avocet Mining PLC
West African Projects
North pit where the mineralised shear zone is up to 80m wide. Drilling and blasting
commenced in 2010 as mining deepened into less oxidised material. The mine plan will
excavate mostly oxidised ore from two main pits and four smaller pits over a seven year
period. This allows for multiple ore sources and blending of ores if required. Each pit
maintains a dedicated, easily accessible waste dump in close proximity to mining operations,
although it is likely that the size and number of open pits may grow as the deposit and
adjacent prospects are more thoroughly explored and developed.
Inata is being mined using conventional open pit methods utilising an owner‐operated
mining fleet. On average, the upper 35m of the deposit is heavily oxidised and can be mined
by free digging. Drilling and blasting of rock beneath this level is performed on 5m high
benches with mining conducted on 2.5m flitches. No final walls have been developed to
date. Interim walls consist of two five metre benches with a 60° degree bench face angle and
a five metre berm. The current final pit designs for Inata North and Central Pits have
maximum depths of 270m, and 170m respectively. To assist with slope depressurization in
the Inata North Pit, sub‐horizontal (5‐10º) holes will have to be drilled into the east and west
walls in the portion of the slope below the projected water table.
The mining of 23.2Mt of ore is presently scheduled to supply, on average, 170,000 feed
ounces of gold per annum. A total of 1.48M ounces will be presented to the mill under the
existing life‐of‐mine plan. No Inferred Mineral Resource is included in this forecast.
Metallurgical test work conducted on drill core showed that the majority of the Inata gold
deposit responded well to a standard milling and CIL process with laboratory recoveries of
93‐95%. Organic carbon, in the fresh and transitional ore zones, has a minor negative effect
on gold recoveries, but testing indicated that this can be largely negated by kerosene
blanking. Avocet Mining’s experience with carbonaceous ores at Penjom, Malaysia, is being
used to evaluate the potentially detrimental effects of carbon at Inata. Leach kinetics
indicated that a moderate sized grind of 80% passing a 106µm allowed good recoveries.
However, a more conservative approach utilising a P80 of 75µm was adopted at Inata. No
gravity circuit is currently employed in the Inata processing facility but is being considered as
an option for the future.
Processing commenced in late 2009 permitting gold to be first poured in December of that
year, and the mine produced 137,732 ounces of gold in the first 12 months of production.
The plant had a design throughput of 2.25Mt/yr. Operating experience and process
modifications have increased the process capacity to 2.7Mt/yr. A conventional tailings
facility is provided, capable of holding a minimum volume of 15.7Mt of tailings waste
material generated from ore processing over the proposed nine year mine life. This facility
has recently been raised to accommodate an additional 3.5Mt (about 12 months of
operational tailings). A second tailings facility will be required to accommodate all of the Ore
Reserves.
All power is generated at the site, supplied by seven Cummins C2250 D5 diesel generators,
with an eighth unit currently being commissioned.
The water supply for mining and milling operations has been established at the Gomdé
Barrage, where a dam has been constructed to impound rainfall falling over a large
catchment area in the months of July to September. This benefits not only the mining
operation, but provides the area with a sustainable water source. The dam has a capacity of
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