Gold has been discovered all over the world. Historically, mines have existed in Wales, Spain, India, Arabia, Italy, the Ural Mountains, as well as South and Central America, the Caribbean and Alaska. However, most of the Gold today is extracted from sites in China, Russia, Australia, the United States, Canada, Peru, Ghana and South Africa.
The Earth’s oceans contain significant amounts of Gold, but the cost of extraction and current technology means these will remain unviable for some time. The Earth’s crust contains just 0.0004 grams of gold per ton and the “low hanging fruit” of easy Gold extraction has been exhausted. Nowadays, extraction is far more complicated than before.
Types of Gold Extraction
Below are the three main variants of mining Gold:
Placer Mining – when Gold deposits are composed of loose material and water or dredging is used to separate Gold from the rest of the material.
Panning – the traditional image of the Wild West Prospector. Panning is a manual technique whereby material thought to contain Gold is placed in a pan submerged in water and shaken. The Gold, as it is heavier, settles to the bottom.
Sluicing – used in small-scale mining a sluice box contains channels designed to catch Gold as water passes through.
Dredging – also usually used in small scale-mining. Small suction machines float on top of the water. These contain a sluice box designed to sort material from the bed below.
By-product Mining – this is where the primary aim of the mine is to extract another metal or ore, but which also extracts Gold. The Indonesian Grasberg mine is actually the world’s largest Gold producing mine even though its primary function is to extract copper. In fact, one-third of all Gold production is from by-product processes from mining copper, lead or zinc.
Hard Rock Mining – this is the main method used by the majority of commercial Gold mines. And it is this that will be focused on below.
Hard Rock Mining
Step 1: Exploration
According to the World Gold Council less than 0.1% of all prospected potential Gold mines turn out to be viable and exploited commercially. Such research and prospecting require a multidisciplinary approach. Geologists, chemists, engineers, computer scientists and geographers, cartographers, seismologists all combine to assess the viability of a potential mine. It can take up to ten years before a decision to go ahead can occur.
Step 2: Mine Construction and Development
Once the decision is made the mine infrastructure and the surrounding area have to be planned. Licences have to be obtained and confirmed. Local populations have to be consulted with and additional infrastructure provided. Furthermore, additional processing equipment may have to be constructed. This entire process can take up to 5 years.
Step 3: Mining
The definition of Hard Rock Mining covers a variety of techniques to mine usually metals, gems or ores. This is in contrast to Soft Rock Mining which is used for salt or coal.
There are two phases. First is the developmental phase. Here, waste rock is blasted or dug out and removed in order to expose where the Gold ore is thought to be.
After this comes production mining where the Gold ore is removed from the ground. Some mines are increasingly automated but there still remains a large human element. Cooling systems are deployed to make the deep mine bearable for the miners. TuaTona mine, in South Africa, for example, reaches down over 2 miles into the Earth. Underground workers locate ore within the rock and may have to use machines or explosives to free it from the rock wall. 1000s of metric tons of rock can be cleared daily. The rock and ore are then sent upwards to the surface for separation.
But this is not the shiny yellow metal, gleaming and polished that is so recognisable. In fact, at this point, this rock and ore is only 60%-90% pure Gold.
Step 4: Processing
This is only the beginning of the journey. The extracted material now needs to go through a number of various processes and iterations before it reaches the purity required by the market. This will be addressed in a forthcoming lesson.