Exploration

Exploration is the search for minerals where nature has deposited them. Technology helps minimize the impact of this search. Using satellite imagery, sensors and computers, geologists survey large areas of land before deciding where to explore in detail. Drilling brings up rock samples from within the targeted area. The samples are analyzed to determine the size and quality of the potential orebody.

Consultation, Environmental Assessment and Financial Feasibility

A decision to develop a mine is made only when exploration indicates the mineral deposit is economically feasible. But that's not the only factor. An environmental assessment is also undertaken to ensure that during operation, as well as on closure, all environmental concerns are addressed and that the site is left in an environmentally acceptable manner. In addition, consultation takes place with community members to explore issues such as economic development opportunities, employment and specific concerns.

Building the Mine

Building a mine is a lengthy and expensive process. Because mines are often in remote locations, infrastructure such as roads, power lines, offices and buildings must be put in place. In northern locations, schedules must be planned around weather conditions, e.g., shipping seasons. Detailed mine plans must be approved by various levels of government. The mining company must also put aside money for reclaiming the land once the mine closes.

Mining

There are two types of mining used to access gold deposits:

• Open-pit mining is used if the gold is close to the surface. This type of mining involves drilling or blasting the ore and then lifting the broken ore onto trucks or conveyors for transportation to the processing plant.
• If the gold is deeply buried, underground mining is used. A vertical shaft or ramp (designed to transport people and/or materials) is first sunk deep into the ground, after which horizontal development takes place at various levels of the main shaft or decline. This allows for further development of specific mining areas where the orebody has been identified. Holes are drilled into the orebody, filled with explosives and then blasted. The blasted “stopes” or “faces” are then cleaned and the ore released is transported out of the mine.

Mineral Processing

Ore samples are taken and examined to determine the processing method needed to remove the gold. The ore is crushed and undergoes various processes. The loose rock is then sent to the appropriate processing location.

Lower-grade ore is broken into small chunks and placed on carefully lined pads where a dilute cyanide solution is distributed over the surface of the heap. The solution percolates through the heap and the cyanide dissolves the gold. This solution containing dissolved gold is then collected.

Higher-grade ore is delivered to a grinding mill, where the it is pulverized to a powder. Depending on its metallurgical characteristics, the ore may be treated in one of three recovery circuits:

• Refractory ore containing carbon is roasted to over 1,000 degrees Fahrenheit, burning off the sulfide and carbon. The product of this process is an oxide ore, which is routed to the leaching circuit.
• Oxide ore is sent directly to the leaching circuit where cyanide dissolves the gold.
• Sulfide refractory ore without carbon is oxidized in an autoclave to liberate the gold from sulfide minerals, and is then sent to the leaching circuit.

In the leaching circuit, the gold is extracted from the solution and deposited onto activated carbon, from which the gold is then chemically stripped. The gold is melted into doré bars containing up to 90% pure gold. The doré bars destined to become bullion bars are transported to a refinery for refining to as close to pure gold as possible.

Reclamation

Gold reserves in a mine are eventually depleted. Reclamation is the cornerstone of every mine plan and is considered the first and last step of the mining process. It involves returning the land, to the extent possible, to its previous natural state. Reclamation activity often includes the removal of buildings, equipment, machinery and other physical remnants of mining; closure of tailings impoundments, leach pads and other mine features; and contouring, covering and revegetation of waste rock piles and other disturbed areas.