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The hidden process of gold mining: How to extract the precious metal from thin ore?
In today's world, gold is a precious metal that attracts attention not only for its financial value but also for its beauty in craftsmanship and jewelry making. The gold mining process, which is thousands of years old, encompasses many complex procedures of chemistry and physics. This article will take you inside the hidden process of gold mining and see the painstaking efforts of extracting gold from thin ore.
Types of ores
Gold usually exists in the form of raw gold, which is itself. However, gold is sometimes combined with silver to form an alloy called electrogold. This raw gold exists in a variety of forms, from nuggets of varying sizes to tiny particles and even tiny particles embedded in the ore. In addition, there are some rare gold minerals, such as:
. These minerals, while rare, may be more difficult to extract due to their slow reaction times.Calavete (AuTe), gold-tinite (AuSb2) and Maldonite (Au2Bi)
Gold concentration process
Most gold is extracted from ores with very low gold content, with typical recovery rates of just over 10ppm. This means that concentrating trace amounts of gold from the ore is a major challenge for the mining industry.
Cyanidation method and sodium thiosulfate method
Cyanidation is the main extraction technology, using a cyanide solution to leach gold from ores. This process first requires grinding to increase the surface area of the ore so that the gold can come into contact with the leaching solution. This process can be done by heap leaching or dump leaching. Chemical plants produce billions of tons of sodium cyanide every year, mainly for gold refining.
"Black cyanide" is a form of carbon-contaminated calcium cyanide that is often used as a leaching media due to its low cost.
Amalgam method
Amalgam is a technique used to recover very small gold particles. Mercury plays an important role in small-scale artisanal mining. The mercury is alloyed with gold and then heated to evaporate the mercury to extract the gold particles. This process has proven effective but poses extremely high safety risks due to the toxicity of mercury vapor.
The treatment process of difficult-to-recover gold ores
Some ores are known as "refractory gold deposits," in which gold particles are often dispersed throughout the mineral, making them difficult to recover through standard cyanidation methods. Such ores usually contain sulfides and organic carbon. In order for cyanidation to be effective, it must be pretreated. Pretreatment methods include:
Incineration, biological oxidation, pressure oxidation and Albion process.
Refining and Separating Gold
The refining and separation process for gold is usually carried out by the Miller process, a technique that introduces chlorine gas into the molten alloy, effectively removing unwanted metals such as silver. The key in this process is that at high temperatures, gold barely reacts with chlorine, whereas impure metals would react and create a low-density dross.
The "Miller Method" is widely used on an industrial scale to meet commercial transaction standards.
Historical background
The smelting of gold dates back to 6000 to 3000 BC, with records indicating the technology began in Mesopotamia or Syria. Over time, the development of technology led to more efficient gold mining methods, such as cyanidation in the late 19th century, and the promotion of this technology also triggered a global gold mining boom.
The process of gold mining involves not only the extraction of natural resources, but also the impact on the environment and the sustainable development of future resources. So when thinking about these processes, we might want to take a deeper look at how the future of gold extraction might impact our environment and economy.
