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Operations
Ridgeway
| Ownership |
100% Newcrest |
| Location |
Orange District, Central Western New South Wales, Australia |
|
Year commenced operations |
April 2002 |
|
General Manager Operations |
Craig Jones |
| Style of mineralization |
Porphyry |
|
Contained metals |
Gold-copper |
|
Resources* |
155Mt @ 0.73 g/t Au, 0.38% Cu for 3.6Moz Au and 580kt Cu |
|
Reserves* |
101Mt @ 0.81 g/t Au, 0.38% Cu for 2.6Moz Au and 380kt Cu |
|
Mining method |
Underground |
|
Processing method |
Flotation & Gravity |
|
Nominal treatment rate |
5.6 Mtpa |
|
Product |
Gold-copper concentrate, bullion |
|
Forecast mine life |
Ridgeway mine transitions to Ridgeway Deeps in 2009/10 |
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* Per 30 June 2010 Mineral Resource and Ore Reserve statement and includes Ridgeway Deeps.
Overview
The Ridgeway mine is amongst the largest underground operations in Australia and recognized in the minerals industry as one of the most efficient underground mines in the world today.
The Ridgeway deposit, discovered in November 1996, lies approximately 500 metres below the surface and 3 kilometres northwest of Cadia Hill. Operations at the Ridgeway mine commenced in 2000 with initial ore processed through the Cadia Hill treatment plant. In April 2002, the Ridgeway treatment plant was officially opened with a nameplate capacity of 4Mtpa. The underground mining rate and concentrator throughput have since been increased to 5.6 Mtpa.
Geology
Ridgeway is the westernmost deposit identified within the Cadia mineralized corridor. The Ridgeway ore body measures approximately 450 metres by 250 metres and currently extends more than 850 metres vertically. The mineralization remains open at depth. It is bounded by a series of shears which form distinct contacts between ore, waste and low-grade mineralization. The Ridgeway lode is sub-vertical and is developed around a monzonite body which intrudes a sequence of Ordovician volcanics and sediments. The gold-copper mineralization at Ridgeway occurs as quartz veins, sheeted quartz sulphide veins and stockworks. The gold occurs mainly as free grains in quartz or on the margins of sulphide grains. The principal copper sulphide minerals are chalcopyrite and bornite.
Mining
The sub-level caving mining method is used where the ore body is mined from the top down using drill and blasting. This allows the overlying rock to cave under gravity as extraction of the orebody progresses downwards. Ore is accessed through a series of horizontal tunnels and dumped into ore passes for transfer to the primary underground crusher. Crushed ore is transported up a 3.5 kilometre decline by a conveyor where it is deposited on surface stockpiles adjacent to the Ridgeway concentrator
The use of the sub-level caving mining method enables Newcrest to cost effectively mine the ore located at depth whilst maintaining low production costs.
In April 2005, Ridgeway successfully made the transition from contract mining to owner operated mining.
Processing
Underground ore is processed in the 5.6 Mtpa Ridgeway concentrator. This concentrator uses similar processes to the adjacent Cadia Hill concentrator with the major differences being the size of the facility which is designed to process higher grade Ridgeway ore.
The comminution circuit consists of a two stage grinding circuit with a 6.5 MW SAG mill and 6.5 MW ball mill. Ground ore slurry from the comminution circuit passes to a conventional flotation circuit to recover gold and copper to a copper concentrate containing elevated gold values. The Ridgeway concentrate is combined with concentrate from Cadia Hill which is pumped as slurry to a filtration plant in the nearby town of Blayney.
A gravity circuit recovers some 25% of the total gold which is smelted on site to produce doré.
Water Supply
Refer to Cadia Hill Operations section.
Future Developments
Ridgeway is in the process of transitioning from the sub-level cave to a block cave beneath the existing mine. Refer to Ridgeway Deeps project.
Key production and cost data for Ridgeway is illustrated in the graphs below.
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