Mining

	Kumtor's mining fleet includes six hydraulic shovels, four front-end loaders and 30 haul trucks

The Kumtor deposit is mined using conventional open pit methods. It currently produces about 15,000 tonnes per day of ore and 220,000 tonnes per day of waste (including ice). The mine operates two 12-hour shifts 365 days a year. Four crews work a 14-day rotation at the site.

Initially, a portion of the ore body was overlaid by a glacial icecap 10 to 30 metres thick. The icecap was removed during the first three years of operation and mining is now focused on ore extraction and removal of the surrounding waste rock. Operations began at a 4,300 metre elevation in 1996 and mining is presently conducted between 4,100 and 3,950 metres elevation.

Mining benches are eight metres in height with three to four benches under development at any given time. Drilling is performed by seven rotary-percussion blasthole drill rigs. Charging the holes is performed with special bulk explosives trucks.

Nine hydraulic shovels and three front-end loaders serve a fleet of 42 haul trucks. All mine equipment is monitored by a computer-controlled dispatch system.

Hydrological conditions are controlled by the presence of up to 250 metres of permafrost. Supra-permafrost groundwater occurs in a thin thaw zone near the surface, active only from July to October. Groundwater volumes from this zone are relatively small and are included with the water volumes handled as surface runoff and glacial meltwater. Surface waters are diverted away from the pit using diversion ditches, sumps and gravity pipelines. Water within the pit is collected in sumps and is pumped outside of the pit limits. The current permafrost level is at about 3,950 metres elevation. The pit excavation will eventually reach sub-permafrost levels, and increased groundwater flows can be expected near the end of the mine's life.

Grade control in the pit is performed by sampling of the blasthole cuttings and sorting according to grade. The ore-sorting program establishes the level of 1.28 grams of gold per tonne as the effective incremental cut-off grade of the operation. At the end of December 2005, the low-grade stockpiles was 1.7 million tonnes with an average grade of 1.4 grams of gold per tonne.

The blasthole assay data are combined into an ore control model that is used to determine the dig lines for the various grade categories and to estimate the monthly pit production.

Milling

	The grinding circuit at the Kumtor mill, which operates at a throughput rate of 5.5 to 5.6 million tonnes per year.

The milling process at Kumtor reflects the fine-grained nature of the gold and its intimate association with pyrite, and consists of crushing, grinding, pyrite flotation, and re-grinding the flotation concentrate. Two separate carbon-in-leach (CIL) circuits recover the gold from the re-ground concentrate and from the flotation tails, with final gold recovery accomplished by electrowinning and refining. The mill was originally designed with a capacity to process 4.8 million tonnes of ore per year but actual mill throughput is currently 5.5 million tonnes per year.

The ore to be milled is managed through a number of stockpiles that receive ore of different metallurgical character and of different grade ranges, thus allowing blending of the mill feed. A gyratory crusher reduces the ore to 100% minus 30 centimetres, fed to a coarse ore stockpile from which it is reclaimed for grinding, first to a semi-autogenous mill and then to a ball mill, which together reduce the grain size to 80% passing 140 microns. A bulk sulphide concentrate representing 7% to 11% of the original mill feed is then produced with a grade of 30 to 50 grams per tonne of gold and a gold recovery of 87% to 92%.

The flotation concentrate is re-ground to 90% passing 20 microns and is thickened to 60% solids, re-pulped with fresh water to 45% solids, pre-aerated for 20 hours and leached for 80 hours in the CIL circuit consisting of five highly agitated tanks in series. In 2005, as a result of continuous improvement initiative, a ultrafine grinding mill or ISA-Mill was installed to grind the concentrate prior to cyanide leaching down to a particle size of less than a 38 µm screen size. The ISA-Mill is an important process in the sustainability of the future KOC operations to maintain higher recoveries as the grade of the ore changes at different stages of on-going pit development.

The flotation tailings with an average grade of 0.5 grams per tonne are thickened to 50% solids and subjected to cyanidation for 10 hours in a CIL circuit similar to the circuit used for the sulphide concentrate.

Gold recovery in the CIL circuits is 30% for the flotation tailings and 90% for the sulphide concentrate. The loaded carbon is stripped and the gold subsequently recovered by electrowinning.

Historically, the overall metallurgical recovery has averaged 79%, but since 1999 has averaged 80.5% and this rate is expected to be maintained in future while mining primary ore.