The business of gold and the challenges it poses

1. FINDING THE OREBODY

AngloGold Ashanti’s greenfields exploration group identifies prospective gold deposit targets and undertakes exploration on its own or in conjunction with joint venture partners. Worthwhile discoveries undergo a well structured and intensive evaluation process before a decision is made to proceed with developing the mine.

• Impact on restricted areas – biodiversity
• Consultation with communities, including interaction with artisanal and small-scale miners (ASM)
• Human rights and security

2. MINING: ACCESSING THE OREBODY

There are two types of mining which take place to access the orebody:

• Underground mining: a vertical or decline shaft is sunk deep into the ground to transport people and mining materials to underground levels from which the orebody is accessed through horizontal tunnels known as haulages and cross-cuts. Further on-reef development is then undertaken to open up the orebody so that mining can take place.
• Open-pit mining: in this situation the ore lies close to surface and can be exposed for mining by “stripping” the overlying barren material.

• Human rights issues
• Dealing with regional health threats
• Fair employment practices and development skills
• Safety and health
• Efficient use of resources – water, energy and other natural resources
• Reducing carbon footprint, preventing pollution
• Human rights and security
• Environmental footprint (landuse/biodiversity)
• Interaction with artisanal and small-scale miners
• Minimising emissions to air
• Land disturbance
• Local economic development and sustainable social investment

3. MINING: REMOVING THE ORE

• In underground mining, ore is drilled and blasted, and brought to the surface
• In open-pit mining, drilling and blasting may also be necessary to break the ore; excavators then load the material onto the ore transport system which is predominantly haul trucks.

• Human rights issues
• Dealing with regional health threats
• Fair employment practices and development skills
• Safety and health
• Efficient use of resources – water, energy and other natural resources
• Reducing carbon footprint, preventing pollution
• Human rights and security
• Interaction with artisanal and small-scale miners
• Minimising emissions to air
• Land disturbance

4. MINING: TRANSPORTING BROKEN MATERIAL TO PLANTS FOR TREATMENT

• Underground ore is brought to the surface by a combination of horizontal and vertical transport systems. Once on surface the ore is usually transported to the processing facilities by surface rail or overland conveyors.
• In open pit operations the haul trucks deliver the ore directly to the processing facilities.

• Human rights issues
• Dealing with regional health threats
• Fair employment practices and development skills
• Safety and health
• Efficient use of resources – water, energy and other natural resources
• Reducing carbon footprint, preventing pollution
• Human rights and security
• Interaction with artisanal and small-scale miners
• Minimising emissions to air
• Land disturbance
• Local economic development and sustainable social investment

5. PROCESSING

Comminution involves the breaking up of ore into small particles so that the contained gold minerals are exposed. This is undertaken by a combination of multi-stage crushing and milling circuits. Recovery of gold can then commence, depending on the nature of the gold contained in the ore.

Free milling and oxidised refractory ores are processed for gold recovery by leaching the ore in agitated (stirred) tanks in an alkaline cyanide leach solution. In this process, ore is crushed and heaped on an impervious or lined leach pad. Low strength alkaline cyanide solution is irrigated over the heaped pad for periods of up to three months. The dissolved gold bearing solution is collected from the base of the heap and transferred to carbon-in-solution (CIS) columns where the gold cyanide complex is adsorbed onto activated carbon.

Gold which has loaded (adsorbed) onto activated carbon is recovered by a process of re-dissolving the gold from the activated carbon (elution), followed by precipitation in electro-winning cells and subsequent smelting of the precipitate into dor? bars. At some operations, by-products are generated, such as silver, sulphuric acid and uranium.

• Minimising emissions and preventing pollution
• Efficient use of resources
• Management of cyanide
• Reducing carbon footprint
• Local economic development and sustainable social investment

6. REFINING

The dor? bars are transported to a precious metal refinery for further processing. In this process gold is upgraded to a purity of 99.5% or greater for sale to a range of final users. High purity gold is referred to as “good delivery” which means that it meets the quality standards set by the London Bullion Markets Association and gives the final buyer assurance that the bar contains the quantity and purity of gold as stamped on the bar.

• Minimising emissions (air quality)

7. MINE-SITE REHABILITATION

Once mining has been completed, operations are ‘closed’ and rehabilitation activities begin to return the land to a productive state. (Rehabilitation is the process of reclaiming mined land to the condition that existed prior to mining or to a pre-determined post-mining use.) Planning for this process is undertaken during the life of mine.

• Rehabilitation and achieving closure
• Post-closure monitoring
• Engaging with communities