Cortez Mine

Overview

The Cortez gold mine is located 100 kilometres southwest of Elko, Nevada, USA. It is a complex of several open pit mines, an underground mine, concentrator and several heap leach pads.

The Pipeline and South Pipeline deposits are mined by conventional open-pit methods. Located next to the existing Cortez Pipeline mine on the Battle Mountain trend, the open pit and underground Cortez Hills mine is expected to be a significant contributor to Barrick as a key, long life, low cost mine.

Cortez employs three different metallurgical processes to recover gold. Lower-grade oxide ore is heap leached, while higher-grade non-refractory ore is treated in a conventional mill using cyanidation and a carbon-in-leach (“CIL”) process. Heap leached ore is hauled directly to leach pads for gold recovery. Carbonaceous mill ore is mined intermittently during the mining of the Pipeline/South Pipeline deposits.

The Cortez Hills underground mine is accessed by twin declines portaled in the old Cortez Gold F canyon pit. The breccia ore zone employs underhand cut and fill mining methods with cemented rock fill as backfill. The top cut of the underground mine will eventually be the bottom bench of the Cortez Hills open pit.

In 2009 Cortez’s production totaled 518,000 ounces of gold at total cash costs of $510 per ounce1. Proven and probable mineral reserves as of December 31, 2009 are estimated at 14.1 million ounces of gold.

The Cortez Hills project was completed in line with its pre-production capital budget and entered production in first quarter 2010, becoming the seventh project in five years that Barrick has delivered on time.

Production at Cortez for the second quarter and first half of 2010 increased by 150% and 170%, respectively, over the same prior year periods. The entire Cortez property is expected to exceed its original production guidance for 2010 of 1.08–1.12 million ounces. Cortez Hills continues to operate under the terms of the tailored injunction issued by the District Court while the Bureau of Land Management completes a Supplementary Environmental Impact Study (SEIS) on three aspects identified by the 9th Circuit Court of Appeals. Barrick continues to expect completion of the SEIS and a Record of Decision to be issued by year-end.

Location

The Cortez gold mine is located 100 kilometres southwest of Elko, Nevada in Lander County. The Cortez Pipeline property is 11 kilometres northwest and the Cortez Pediment property (which includes the Cortez Hills deposit) is 4 kilometres southeast of the original Cortez milling complex.

The Cortez property covers approximately 2,800 square kilometres on one of the world’s most highly prospective mineral trends.

Located next to the existing Cortez Pipeline mine on the Battle Mountain trend, the open pit and underground Cortez Hills mine is expected to be a significant contributor to Barrick as a key, long life, low cost mine.

Geology

There are a number of different occurrences of gold within the Cortez properties. They are typically finely disseminated, Carlin-type occurrences with sub-micron sized gold mineralization found in a variety of sedimentary rock formations. The majority of the reserves are hosted in siltstone of the Silurian Roberts Mountain Formation. Most gold ore is oxidized; however, it is not uncommon for some gold to be associated with carbonaceous or refractory rock. Mineralization is controlled by a low-angle shear zone and is localized by high-angle faults.

The Pipeline Deposit, 6 miles NW of the plant site is estimated to contain more than 2.6 million ounces of gold. The discovery hole was drilled to 1,000 feet, encountering mineralization approximately 490 feet below surface. The hole returned assays of continuous oxide mineralization averaging 0.31 oz/ton Au over 120 feet. Drilling to outlined 11,300,000 tons of material grading 0.237 oz/ton Au at a 0.05 oz/ton Au cut-off grade.

Mining & Operations

Barrick currently runs a high volume, highly efficient, capital intensive mining operation.

The Pipeline Complex has helped Barrick become one of the world's lowest cost gold producers. The mine's capacity is 250,000 tpd.

Conventional open-pit mining methods are used with a capacity of 70Mt/y. Pit wall slopes vary from 34° to 50°. Mining is carried out with electric shovels, a hydraulic shovel and haul trucks.

A fleet of miscellaneous equipment includes rotary/hammer blasthole drills, wheel loaders, bulldozers, graders and water trucks.

Cortez won the Mining Operation of the Year award at the Mining Journal's Outstanding Achievement Awards in 2004.

At the underground Cortez Hill mine, the breccia ore zone employs underhand cut and fill mining methods with cemented rock fill as backfill. The top cut of the underground mine will eventually be the bottom bench of the Cortez Hills open pit.

Processing

Three different metallurgical processes are employed for the recovery of gold with the process chosen influenced by ore grade and metallurgical character. Lower grade oxide ore is heap leached, while higher grade non-refractory ore is treated in a conventional mill using cyanidation and a CIL process. When carbonaceous ore is processed, it is first dry ground, and then oxidized in a circulating fluid bed roaster, followed by CIL recovery in Mill #1. Currently the roaster is on care and maintenance. Capital cost of the complex, including mine waste stripping from the refractory orebodies, was approximately US$34 million.

The new Pipeline concentrator has a throughput of 8,650t/d, having been designed to handle various types of oxide ore from the Pipeline and South Pipeline orebodies.

Its flowsheet consists of primary crushing, autogenous/ball mill grinding, carbon-in-leach and carbon-in-column gold recovery systems, together with carbon stripping, reactivation and gold refining facilities. Low-grade, run-of-mine oxide ore is heap-leached, with gold-bearing carbon from this section being returned to the main concentrator for gold recovery.

Environment & Community

Environment and Community - Barrick is guided by their commitment to responsible behavior. In practice, this translates into bringing long-term benefits to the communities where they operate and fostering a culture of excellence and collaboration among employees and contractors.

Ongoing environmental monitoring, at Cortez, provides feedback on the effectiveness of our environmental controls. Company environmental specialists routinely monitor the land, air and water on, and adjacent to, the property. Monitoring results are regularly reviewed and areas for improvement are identified. When needed, performance and site activities are adjusted to ensure environmental protection. Corporate environmental audits are conducted regularly, usually every two years, to review the effectiveness of the mine's environmental management systems.

At Cortez water is a valuable resource and, as such, every effort is made to conserve water and minimize the impacts of its use. Cortez obtains water exclusively from pit dewatering. Specific water conservation activities at Cortez include using instrumentation to measure and control water use and recycling water through the mine's processing systems.

Cortez has developed a number of stewardship programs to protect animals from the hazards of mining activities, and to mitigate impacts to habitat around the mine site. For example, the mine's process ponds are tempting stopovers for migratory waterfowl in this arid region. In order to prevent birds from using the ponds, hollow black plastic balls, about the size of a softball, are placed on the processing ponds. These 'bird balls' float on the surface, covering the pond entirely and camouflaging it from waterfowl.