Many facets of the precious metals industry are incredibly fascinating to learn more about. Extracting gold, for example, is a very intriguing process which most people know nothing about. There is a good reason why this precious metal is rather difficult to extract, after all.
Extraction Isn’t Mining
When it comes to obtaining gold, most people won’t look further than the mining process. Digging up gold from the earth is a very labor-intensive task, but it is also only the first step along a much longer chain of procedures. Mining gold and extracting it from its ores are two very different things. It is crucial to know the difference.
Over the years, there have been a few different processes to be used for extracting gold. Some are deemed safer than others, although things have certainly improved over the past few decades. Depending on the method used, the results may also vary significantly.
The Different Mining Techniques
One of the more approachable ways of extracting gold is to conduct placer mining. It is this method that has gotten rather famous. Users dig up dirt, pan it in a stream of water, or put it through a dedicated sluice box. This allows for the direct recovery of nuggets and flakes.
Another commonly used technique – at least until the 1960s – is known as hydraulic mining. Through this method, miners would use high-pressure water jets to break down ore deposits. It was a time-consuming process, and one that could be deemed relatively dangerous as well. It has lost a lot of its initial appeal.
Extracting the Gold
Recovering nuggets and flakes is fine and dandy, but it’s not always the most efficient. In fact, most of the gold extracted from the earth requires at least one additional process to remove unwanted ores and minerals.
Heap leaching, for example, is a process that requires ore to be crushed and agglomerated. It is often used for low-grade oxide deposits. High-grade ores will resist the cyanide used in the leaching process, whereas everything else will either burn off or disappear completely. It is worth noting that leaching only occurs if gold cannot be concentrated for smelting.
Using cyanide has proven to be a successful and popular solution. Initially invested by John Stewart MacArthur, Dr Robert Forrest, and Dr. William Forrest, the suspension of crushed ore in a cyanide solution yields remarkable results. In fact, back in 1887, the trio managed to separate up to 96% pure gold. This method has been refined since, although the recovery percentage has not changed all that much.
Another process in this industry comes in the form of froth flotation. It is utilized when gold is present in the ore as coarse particles. This occurs when one finds gold along with sulfide minerals, such as pyrite. Recovering the gold from sulfide concentrates will often require further processing, but froth flotation can make a notable difference.
It is equally possible that gold is recovered as a by-product. As odd as that may sound, it is possible to mine copper, and find gold by accident. Separating the precious metal from the base ore is done through electrorefining.It removes the use of a current to be passed from an inert anode through a liquid leach solution containing the metal.
Refractory Gold Processing
One “odd duck in the pond” is refractory gold processing. This method is only used when the gold particles are too fine to be recovered by cyanidation or other standard processes. Recovering the gold through this method requires pre-treatment of the ore to make cyanidation effective.
As part of refractory gold processing, the ore will usually contain organic carbon, sulfide minerals, or both. Depending on the pre-treatment process being used, this can be a very time-consuming venture. Companies specializing in gold recovery will often have used refractory processing one or twice in recent times.