Market Survey on Copper - Indian Bureau of Mines

Open-pit mining
The Ujina and Huinquintipa zones were mined first, with a transition to the
Rosario orebody completed during 2004. Stripping at Rosario began in 2002. The
stripping ratio at Ujina averages 4.4:1 (waste: ore) with a 15m bench height.
Huinquintipa is somewhat smaller. The design mining rate of 360,000t/d of rock was
achieved in Year 1, involving the blasting of 750,000t of material every two days.
In 2008, Xstrata Copper announced a 28% increase in the total estimated
mineral resource at the mine, representing the equivalent of an additional 11 million
tons of contained copper metal from 2007 resources.
Processing
The processing area consists of both oxide and sulphide plants. Oxide and
mixed ores are treated by heap-leaching, solvent-extraction and electro-winning (SX-
EW). Sulphide ore is crushed, ground and treated by flotation.
Run-of-mine sulphide ore enters the primary gyratory crusher prior to transport
to two parallel grinding circuits, each consisting of a Semi Autogenous Grinding mill
and a ball mill. Secondary closed circuit grinding includes cyclone classifiers, from
which the overflow feeds the flotation circuit. Flotation concentrate is thickened to
50% solids for slurry transport in a 200 km-long pipeline to Punta Patache, 65km
south of Iquique, where it is thickened and filtered before shipment worldwide. An
expansion to the concentrator was completed during 2004.
Run-of-mine oxide ore is reduced to -10mm by three-stage crushing. The fine
ore is agglomerated with sulphuric acid and water before being conveyed to the leach
pads. Copper is recovered from the pregnant leach solution in the solvent-extraction
plant, where the copper is stripped using organic solutions; the stripped liquor is then
returned to the leach pads for re-use.
The strip solution is cleaned using dilute acid and flotation, and is filtered prior
to the electro-winning phase, where the copper is plated onto electrolysis cathodes.
These are stripped by the Kidd process on a seven-day cycle, the cathode copper
being transported by road to Iquique for export.
Production
In 2005, Cia Minera Doña Inés de Collahuasi produced 488,600t of copper in
concentrate, plus 68,600t of cathode copper. In December 2005, the company
commissioned a US$36m molybdenum recovery plant that has a capacity of 7,500t/y
of contained molybdenum.
In January 2008, the company announced an upgraded mineral resource of 5.19
bn tons at an average grade of 0.83% copper, including, for the first time, 746 m tons
at a grade of 1.06% from the Rosario Oeste deposit.
This compares to the previous mineral resource of 4.05 bn tons at an average
grade of 0.80% copper. The mineral resource includes ore reserves of 2.20 bn tons at
178
Contd…..