Cripple Creek & Victor

Overview

Located in the state of Colorado in the United States, Cripple Creek & Victor Mining Company's (CC&V) Cresson Project is an open-pit operation which treats extracted ore through a heap-leach pad, and is one of the largest in the world.

CC&V has been mining gold in the Cripple Creek Mining District (District) since 1976. On June 30, 2008, AngloGold Ashanti consolidated 100% ownership in CC&V.

The Cripple Creek Mining District was mined historically in multiple underground operations until the 1960s. Mining activity then ceased for approximately a decade. Small-scale surface mining using the heap-leach gold recovery method began in 1971 followed by large-scale surface mining, which grew with the start of production at CC&V’s current mining operation, called the Cresson Project.

Engineering for the modern Cresson Mine began in 1993.  Obtaining the various permits necessary to mine, ensuring compliance with applicable federal, State, and local requirements was completed in 1994. 

CC&V is a low-grade, surface mining operation. The ore is treated using a valley-type, heap-leach process with activated carbon used to recover the gold. All solution is continually re-circulated. The resulting doré buttons are shipped to a third-party refinery for final processing. Under current permits, mining at current production rates will continue into 2016, with gold recovery carrying on for at least another four years, followed by final reclamation and closure.

Location

Located in the state of Colorado in the United States, the Cresson-Victor district mines consist of more than 2,177 hectares of patented mining claims in and around the Cripple Creek Mining District of Teller County, Colorado and include most of the principal formerly-producing mines of the Cripple Creek district. 

The Cripple Creek & Victor mining operations are 25 km east of Colorado Springs and in between the communities of Cripple Creek to the northwest and Victor to the south.

Geology & Mineralization

The Cripple Creek gold deposits occur within a seven square mile (18 sq. km), 30 million year old, volcanic-intrusive complex (diatreme) that erupted and intruded through rocks that are over one billion years old. The diatreme-intrusive complex is 6.4 km long and 3.2 km wide. The rocks within the complex consist mostly of breccias, dikes, sills, and flows with minor amounts of fossil-bearing lake sediments, sandstones, conglomerates, and fresh-water limestones.

The Cresson is named for the historic underground mining operation of the same name. The Cresson is famous for the great gold find of the District, the “Cresson Vug.”  A vug is a cavity in the rock, lined with crystals somewhat like a geode. The Cresson Vug produced 60,000 troy ounces of gold that was essentially picked from the walls of a room sized void encountered about 1,200 feet below the surface in 1914.

The gold mineralization followed the emplacement of the volcanic rocks and may have occurred over a time period that lasted as long as two million years. Most of the gold was localized along major structural zones within the volcanic complex. The ore bodies occur as (1) deposits of rich, narrow, gold-telluride veins with quartz, pyrite, and fluorite and (2) deposits of low-grade, disseminated, microcrystalline, native gold attached to pyrite. Most of the gold mined in the early days of the district came from the high-grade gold telluride veins.

As of December 2011, proven and probable reserves stood at 247.38 million tonnes grading 0.79 g/t containing 6.25 million ounces gold.

Mining & Operation

The active mining process begins with the drilling of blast holes, approximately 40 feet deep and 16 to 22 feet apart. The drill holes are located by Global Positioning System (GPS) mapping technology. The drill cuttings are sampled to confirm gold content.

Controlled blasts of the drill holes break the rock and minimize movement. Controlled blasts help limit ground vibrations that are carefully monitored to ensure the vibrations are within strict permit limits.

The broken rock, called "muck," is surveyed and marked with flags to indicate gold-bearing ore and non-gold bearing rock referred to as "overburden."

Large dump trucks are then used to move the ore to the primary crusher for processing. The overburden is backfilled to previously mined areas or is moved to engineered storage areas.

In 2011, gold production increased to 267,000 oz from 233,000oz in 2010. A total of 20.3Mt of ore was placed on the heap-leach pads.

Processing

Ore is processed at the two-stage crushing and screening facility and hauled to the Valley Leach Facility (VLF).

The VLF is a double-lined, and in some areas triple-lined, zero-discharge area where the gold is recovered. A dilute solution of sodium cyanide is applied using agricultural-type drip irrigation tubes, which are buried under the crushed rock surface to dissolve the gold. The gold-bearing solution is captured at the bottom of the lined area. The solution containing the gold is called "pregnant solution."

Gold is recovered from the pregnant solution with a carbon absorption process. The gold laden carbon is processed to create a gold-rich mud. After the gold is recovered, the solution with no gold, called "barren solution," is reconstituted and then re-circulated to the VLF to repeat the gold recovery process.

The gold-rich mud is sent to the refinery furnace and heated to separate the gold and silver from any non-metal substances. The resulting 98% gold-silver mixture is called "doré" (daw-rey). The doré is shipped to a specialized refinery to be processed into 99.999% pure gold or 24 karat.

 In 2011, the Cripple Creek mining complex produced 267,000 oz gold at US$564 per ounce total cash cost from 20.3 million tonnes ore processed on the heap leach pads.

Environment & Community

CC&V  is committed to reclaim the land to a beneficial use for grazing and wildlife habitat, by planting grasses, legumes, and forbs, and also
through the transplanting of trees and shrubs.

To ensure that the lands are reclaimed according to the approved reclamation plan, State law requires posting of adequate financial warranty to fully fund reclamation through the State, if that should ever be required. Upon implementation of the plans approved in 2009, the financial warranty for the project will $98 million and this warranty is secured through a letter of credit  payable on demand to the State of Colorado. Only when stages of the reclamation are completed and approved is the warranty reduced.

CC&V continued to be recognised as a Gold Leader in the State of Colorado’s Environmental Leadership Programme, the first mine in Colorado to attain that level of recognition. In addition, CC&V’s Environmental Management System was again recommended for continued certification under the ISO 14001 standard. In September 2010, the operation was recognised by the International Cyanide Management Institute (ICMI) to be recertified “In Full Compliance” on all nine principles of the International Cyanide Management Code (ICMC). No reportable environmental incidents took place in 2010. 

Reclamation is to take place concurrently with mining through 2025. Some reclamation work would continue through 2030.

Over 430 employees earning an average annual compensation of $70,000 were on the payroll in 2011 for a total of $32 million including an excellent benefit package.