Brief Introduction: So, we want to introduce mining technologies to unfamiliar business professionals who desire to understand its implications and effects on the global economy.
The Golden Business: Improvements in the process of gold mining
written by Andrew01
YouTube. “Gold – How its made.” YouTube. 17 Nov. 2008. Web. 19 Aug. 2017. <https://www.youtube.com/watch?v=MyOKNR1JCs0>
Gold is one of the most precious metals in the world, being exceeded in price only by few metals such as rhodium, platinum, and plutonium. It is also a rare metal, hence the reason why gold mining is highly sought in our days.
Gold extraction at present can be done through various processes (depending on the mineralogical composition of the host rock), including gravitational concentration, mercury-based amalgamation still used in developing countries, and cyanide, Which is the modern gold mining standard.
The paradox of this method lies in the fact that, although it is the most effective of what has been known so far, it comes “packed” with some risks because of the toxicity of the substances used, which raises controversy and sometimes vehement protests. In some countries it is forbidden; Other countries have banned it and then reverted to the decision (for example, Greece), and in many others it is widely used – with necessary and mandatory precautions – because it can not challenge efficiency: it can be Mined gold minerals, including those in which gold is found in complex combinations, from which it would be impossible to separate otherwise.
The basis of this method is a chemical phenomenon known for over 200 years: the fact that gold could be dissolved in aqueous cyanide solutions was discovered in 1783 by Swedish chemist Carl Wilhelm Scheele. But the practical use of this particularity of gold began only in the next century.
The process was set up in Glasgow in 1887 by chemist John Stewart MacArthur, funded by the brothers Robert and William Forrest. Since then, the process – called MacArthur-Forrest – has been widely used due to its great effectiveness. With its help, up to 97% of the gold contained in the ore can be extracted (depending on the conditions) (although typically about 80% yield) compared to 60-75% that could be extracted The method of amalgamation (which, moreover, also presents high risks due to mercury toxicity.)
Thus, it was profitable to extract gold from low-gold deposits. And with gold, other metals such as silver and copper could be extracted from the same deposits, which made the process even more cost-effective.
From ore to golden ingot
The process begins with the extraction of the ore, which involves the dismantling of the rocks (blasting), which is done today with the help of explosives. Gold mining technology improvements play an important role here.
The extracted ore is transported to the processing plant, where it is shredded in several stages: a rough crushing, crushing, and then milling in special mills. The purpose of these operations is to expose a larger area to the dissolution of cyanide.
Next is the chemical, which gave the name of the method: the mineral thus prepared is treated, in tanks (special tanks) with a solution of sodium cyanide, a stage called lees. (The cyanide, transported in solid state for safety reasons, is dissolved in water on site at the processing plant to obtain the leach solution). Cyanide dissolves the gold contained in the ore, forming compounds called aurocians.
Then, activated carbon is added to the tanks, a porous material that has the property of adsorbing aurocyanide on the large surface created by the existence of pores. (Adsorption = the process of fixing molecules of a gas or liquid on the surface of a solid body.)
By treating the coal with a solution of hydrochloric acid, the mixture of adsorbed substances, which contains gold, is “washed” out of the pores (eluted in technical language). Coal is thus recovered and can be reused.
There follows the stage in which things start to get the finality, in which, from an amorphous mixture of sorts of substances, finally appears gold. It is separated by electrolysis, then melted, molded and … here! A brilliant golden ingot is a reward of passing through this complicated extraction process.
But what about cyanide? It is, in the eyes of the public, a great danger, and worry is not meaningless. Sodium cyanide is an extremely toxic substance and no precautions are taken in connection with its use are superfluous.
Thus, in Europe and USA, besides the directives dealing with the issue of toxic waste and hazardous substances in general, a special directive, developed in 2006, regulates the use of cyanide in the extractive industry, requiring the strict observance of certain parameters and clearly stipulating what And what mining companies can not do with cyanide.
The extractive industry, in turn, has developed and complies with an international code – the International Cyanide Management Code – a voluntary program (self-help if you want) that promotes responsible use of cyanide in gold mining to minimize environmental and health impacts people.
The technological flow at the processing plant also includes, in its final stages, a cyanide neutralization operation (denocivization, as it is called in the specialized language) through an oxidation process that greatly reduces the cyanide concentration in sterile.
What remains – the processing tail still containing a certain amount of cyanide, considered harmless to humans – is stored in tailings ponds protected by solid dams. Here, over time, cyanide concentration falls naturally, cyanide naturally decomposing, under the effect of light and air, into harmless compounds.
Ninety percent (90%) of the gold extracted today from gold minerals is extracted through the MacArthur-Forrest process. Among the great mines where it is applied are:
Mina Martha – a very productive gold and silver mine in Waihi, on the northern island of New Zealand (pictured above). In 1878, two prospectors discovered gold in this region; Industrial operations began in 1882. In 1952, the mine was closed due to the imbalance between production costs and the gold price on the international market. But in the 1980s, exploitation resumed and continued today, with operations contributing 25-30% to the local economy. Kittilä Mine, northern Finland, is the largest gold mine in Europe and one of the newest. Production began in 2008, and the mine can produce 4 inches of doré of 23 kg piece, per week. (The desired ingots are semi-gold gold bars, in
Kittilä Mine, northern Finland, is the largest gold mine in Europe and one of the newest. Production began in 2008, and the mine can produce 4 inches of doré of 23 kg piece, per week. (The desired ingots are semi-gold gold bars, in fact, an alloy of gold and silver, which are sent to refineries to purify gold.) Gold ore often contains silver, and the two metals are extracted Together with the cyanide method, being subsequently separated into refining plants.)
The Fort Knox mine in Alaska, USA, produces over 10,000 kilograms of gold annually, processing 45,000 tons of ore per day.
From washing golden sand in simple wood vats or sifting through primitive sites to modern mining techniques that require advanced chemistry knowledge, gold extraction has gone a long way marked by spectacular technological leaps, deep influences on nature, phenomena Specific social and irreversible historical changes.
For thousands of years, gold has been … simply gathered. One of the few metals found in the native state, it was found in large quantities in certain parts of the world (including in Transylvania) in alluvial deposits, in the alluvium of some rivers (sometimes former rivers, watercourses Sinking in the meantime, but leaving large accumulations of alluvial material in place, carried by water and accumulated for many millennia). The metal of these deposits comes from the golden wreaths of the mountains; It reaches the water following the erosion process and accumulates in the sand, mud, gravel in the flowing water. Gold is here either in the form of bulgarians, called nuggets, or – most often – only as small particles, mixed among sandblasts.
From here, gold could be extracted by purely mechanical, technologically simple techniques, even if they required a lot of work.
These methods were based on the specific weight of gold, much larger than the surrounding material (sand, for example), which made the gold particles deposit and separate from the useless material.
Depending on the degree of civilization, the technological level of the respective crops, even in ancient times, gold was exploited on a large scale by mechanical methods. The Romans, for example, had developed in the last century BC. And the first century of our era, very efficient gold mining systems (which, of course, required the work of a huge number of slaves) and which involved works of enormous scale:
Deviating courses of rivers so that they wash the soil in certain regions to unravel the golden phylons; The burning of some land, followed by flooding with water; The alternation of temperatures caused the cracking of the rocks, which could easily be broken by iron tools by humans and then dislocated by means of pressurized water.
The construction of aqueducts through which water was brought in large quantities and used to displace the rock layer.
Underground mining, by digging entire miles of galleries to remove the gold from the strands.
Old, but still current methods
But let’s start with the simplest: the handiest method for a miner working on his own was the daily washing of thousands and thousands of “gates” of water mixed with sand and golden gravel, taken out of the river. A simple wooden pot – called a chaise-hat in the Apuseni Mountains – or metal used to serve this mechanical, repetitive work, and whose effectiveness depended not only on the miner’s workmanship, but also on the gold content of the river’s sand and, to a great extent, .
It was one of the favorite methods of the thousands of miners who headed for California during the historic “golden go-go” of the mid-nineteenth century, miners who were later called “forty-niners” (from forty – nine – 49, 1849 being the peak year of Californian gold).
Even today, this ancient method, which has the advantage of simplicity, is still practiced on a small scale in some countries (Madagascar, Ghana, Brazil, for example) the only important change is that the wooden or metal vessel is often replaced by a plastic. (If in these countries these miners do this, for a living income to them in developed countries, instead, the golden gathering through this method is a hobby practiced by a small number of enthusiasts who, in the week -ends and holidays, standing with the water in a river, and washing and washing thousands of bowls of water, hoping to discover the golden golden nugget as the first that any gold seeker dreams of.)
The upper level of this method was the use of large troughs or ramps instead of vessels, through which the water was mixed with golden sand, the gold deposited at the bottom of the trough and then carefully gathered. The gutters were sometimes lined with woolen fabrics to retain the gold; Sometimes they had ditches on the bottom that held the precious metal particles.
And this method has enjoyed popularity for hundreds of years and is still being used in improved versions in Alaska, for example.
Hydraulic mining was a method applied by the Californian miners in the nineteenth century: the water was run through narrower channels, gutters, and pipes, the pressure rising constantly until true water cannons were obtained, with which the miners effectively eradicated the soil Alluvial, rich in gold, channeling the mixture of water and gravel onto the gullies where gold was deposited.
Although very effective, the method has a catastrophic environmental impact: reshaping the relief (entire hills formed in millions of years were crushed by water), and the sediment-rich water resulting from these exploits reached rivers, clogging them or altering their course, sometimes even contributing to the floods.
Gold is still quite found on the planet, but most often mixed with other metals and non-metallic elements, in sometimes complex combinations in the form of gold ores. Thus began one of the revolutions in the field of extraction methods: by switching from the mere addition of native gold, present in sediments, by purely mechanical methods, to its separation by chemical methods from ores.
Ores can be collected either through open-pit mines or through underground mines. Most of the gold extracted today comes from the treatment of ores by chemical methods.
Gold has, among other peculiarities, that it is very difficult to dissolve or, more correctly, soluble in very few substances. In fact, this very low chemical reactivity is one of the reasons why gold has always been so valued, for it is able to endure the passage of time and the action of environmental factors without losing its shine.
One of the few substances in which gold can dissolve is mercury – the result being an alloy, the gold amalgam. It’s not about a chemical combination, but about a physical process – mixing the atoms of the two metals.
In fact, the gold ore was crushed and mixed with mercury, which, having a great affinity for gold, extracted it from combinations with other elements, forcing it to combine it with mercury. The resultant amalgam was heated at high temperatures, which led to vaporization of mercury, leaving behind gold – an impure gold, usually mixed with other metals. This gold was then subjected to a refining, purification process by which the impurities were removed and the gold was separated from other precious metals or not.
The amalgamation method has been the basis of gold extraction technologies for several centuries and is still used in developing countries in small exploits. It is relatively simple, but polluting and dangerous due to mercury toxicity. Besides, it does not remove everything that would be removed from the gold miners but leaves behind gold minerals that would have an interesting economic value if they could be extracted.
This is how the need for a new technological leap emerged – a new way to capitalize gold mines. And this was the cyanide method.
This method, developed by the Scottish chemist John Stewart MacArthur, began to be applied in 1887. You will read about him in the next article; I dedicated a separate article as it is the method currently applied in the most productive gold mines of the world. Although surrounded by great controversy due to the potential danger associated with toxic substances used in the process, it can not be challenged by this method, however, efficiency, which is why it has become the standard in modern gold mining.
In conclusion, present mining is safer than ever, and it can actually be a profitable business idea. Considering the rising price of gold and it’s a rarity in times of financial crisis, those who can afford to invest in a new gold mine will rejoice from constant profit in the upcoming years, as long as the investment is well thought out.