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.
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.
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.
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.