The Cortez Gold Mine, located in Lander and Eureka County, Nevada, is a major gold mining and processing facility situated approximately 63 miles southwest of Elko. This joint venture, primarily owned by Barrick Gold Corporation (61.5%) and Newmont Corporation (38.5%), operates under Barrick’s management. The complex includes the Pipeline, Crossroads, and Cortez Hills open-pit mines, along with the Cortez Hills underground mine.
Historically, the Cortez Mountains have been mined since 1862, initially for silver until the 1940s. Cortez Gold, established in 1968, operated until 1976. The Cortez mill was reopened in the early 1980s, utilizing feed from the nearby Horse Canyon deposit. The 1991 discovery of the Pipeline orebody, a significant find, led to the construction of the Pipeline Mine and mill by the Cortez Joint Venture in 1996. This complex yielded over one million ounces of gold annually from 1998 to 2005.
In 2002, the Cortez Hills deposit was discovered, with underground development initiated in 2006. Barrick Gold acquired a 60% stake in Cortez in 2006 and obtained the remaining 40% from Rio Tinto in March 2008. Ore from the mines undergoes treatment at an on-site oxide mill and leach pads, while refractory ore is transported to Barrick’s Goldstrike operation for processing. The Cortez Gold Mine’s rich history, spanning exploration, discoveries, and ownership changes, solidifies its status as a significant player in the gold mining industry.
Cortez Gold Mine: Overview of Operations and Mining Techniques”
The mining operations at the Cortez Gold Mine employ various techniques for extracting ore from different deposits. The Pipeline and South Pipeline deposits are currently undergoing traditional open-pit mining, while the Cortez Hills deposit will be mined using a combination of open-pit and underground techniques.
Surface mining involves hauling rates of 350,000–400,000 short tons per day, combining ore and waste. With the commissioning of the Cortez Hills open pit, these rates are expected to increase. The current stripping ratio is 3:1, and ore from open-pit mines is transported on the surface using 400-short-ton Liebherr T 282 B trucks. Cortez owns 24 of these trucks, accounting for 10% of the total sales worldwide.
For underground operations at Cortez Hills, parallel declines measuring 16 feet wide by 18 feet high and extending 10,000 feet are utilized. Crosscuts connect declines every 500 feet, with ramps driven at a 6% grade. These declines serve to transport ore from stopes to the surface and provide ventilation for mining operations. The declines are accessed through portals on the wall of an old open pit.
The underground development incorporates welded wire mesh and shotcrete with swellex bolts for ground support. Open stopes are backfilled with waste rock from the open pit, hauled down the decline by empty ore trucks returning from the surface and mixed with cement underground. The potential for utilizing paste backfill, similar to Barrick’s Goldstrike Mine, is considered, providing a potential simplification for the backfill process.
Upon full operation, the Cortez Hills underground mine is estimated to have up to twelve production faces producing 1,200 short tons per day of ore in 2009. These mining operations showcase the complex and comprehensive approach employed at the Cortez Gold Mine to extract and process gold from various deposits.
Processing Operations and Environmental Considerations at Cortez Gold Mine
Processing Operations:
- Pipeline Deposits: Ore from the Pipeline deposits undergoes processing through cyanide heap leaching or milling at the Pipeline mill. Low-grade open-pit ore is heap leached without crushing at operational leach pads. The larger leach pad covers 3.6 million ft² with a flow rate of 20,000 US gal/min, while the smaller pad, connected to the Pipeline mill, has a flow rate of 6,000 US gal/min. Higher-grade ore is processed at the Pipeline mill using CIC/CIL (carbon in column/carbon in leach) methods.
- Cortez Hills Deposit: Low-grade ore from the open pit at the Cortez Hills deposit undergoes heap leaching at dedicated pads on-site. Ore from the underground mine is mixed with higher-grade open-pit ore and transported 10 miles to the Pipeline mill via the largest overland conveyor in Nevada.
Environmental and Social Considerations:
- Environment: Barrick invests in environmental efforts, including relocating a road through Cortez Canyon at a cost of US$15 million, reforesting hillsides, and removing an obsolete roaster. The company collaborates with agencies to revegetate old waste dumps by placing alluvium over waste rock and planting local vegetation.
- Water: In water-scarce Northern Nevada, the mine pumps pit water from aquifers to ranch land to reintroduce it into the groundwater supply. The mine manages contact and non-contact water streams, recycling and reusing contact water within the mining operation, while non-contact water is pumped off-site.
- Native Americans: The Timbisha Shoshone Tribe opposes the Cortez Hills expansion, citing irreversible damage to the land and hindrance to religious practices. A preliminary injunction by the 9th Circuit addresses concerns about environmental damage and restrictions on the religious freedom of the Western Shoshone, particularly focusing on Mount Tenabo’s significance in their culture.