The process of production of gold using mercury is one of the oldest gold extraction processes. The process is considered dangerous to human beings, animals, and the environment. However, extraction of gold from rocks is best done using mercury, unlike alluvial gold that is extracted using other methods. In spite of the fact that the utilization of mercury in mineral extraction is opposed in many nations, mercury amalgamation remains the favored technique utilized in artisanal mining (ASM) activities to extract gold from rocks. According to ( Gibb & O'Leary, 2014), t he major reasons that mercury is highly used by ASM gold miners are that mercury is easy to use, accessible, economical to use, and miners do not mind the associated health hazards.
Prior to further exploration of the aforementioned method of gold mining, it is integral that gold and the history of gold mining in the global platform is explored. From antiquity to contemporary times, gold is deemed to be one of the most expensive and rare metals globally ( Malm, 1998) . Gold is one of the first metals to be mined because the metal exists in a native form; it is not combined with other metals. The motivation to mine gold was associated with the vast usage of the metal as well as the fact that it is imperishable and beautiful. Artisans in the ancient world used gold as a decorative metal; its applications ranged from the decoration of tombs sculptures, and temples as evidenced by gold objects found by anthropologists, some being more than five thousand years old ( Malm, 1998) . One of the most iconic gold sculptures of the ancient world found by anthropologists is the gold statue of an Egyptian ruler, Pharaoh. Furthermore, mines in antiquity were compelled to mine gold because it was presumed to be preferred medium of exchange. As a result, the fact that gold could be used as a medium of exchange across empire boundaries, trade between different groups of people blossomed.
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In a bid to understand why some mining techniques are deemed effective in the extraction of gold over other approaches, it is integral that the properties of gold is explored. Gold is associated with an alchemistic term “noble” because the metal does not undergo oxidation under room conditions. The low oxidation potential of the metal allows it to remain pure under ordinary conditions. In the physical sense, metal is a sun yellow metal. However, gold can be combined with silver, nickel, copper, tellurium, and iron to create a myriad of color hues ranging from orange-red to silver-white.Moreover, pure gold is soft, malleable, and the most ductile metal across the board ( Malm, 1998) . The specific gravity of gold is 19.3. On the other hand, the mercury that is often used in the extraction of gold has a specific gravity of 14.0. The extraction of gold from rocks and other metallic impurities is made possible because of the differences in density. To be precise, the density of gold is 16 to 18, while the density of surrounding rocks is 2.5 ( Malm, 1998) . The density differences allow gold to be concentrated and ultimately separated from silt, clay, salt, and gravel using collection methods such as the use of a gold pan.
Mercury is a metal with exceptional properties that give it a wide variety of uses. For instance, mercury exists in liquid form at standard air pressure and room temperature. Just like water, it is a powerful solvent for many substances on account of its chemical properties. mercury's atomic structure makes it a viable solvent of most metals ( Coulson, 2012) . Also, mercury has a high affinity for gold as is evidenced by the fact that when mercury is added to a gold-containing material, mercury and gold form an amalgam. These properties combined with the low breaking point make mercury useful for removing gold from mineral in the process of amalgamation and distillation of gold. The process of gold production from rocks starts with crushing of rocks before the amalgamation process.
Crushing the Gold-Bearing Rock
Unlike alluvial gold, which is found at exceptionally little pieces on river banks, gold-bearing rocks must be extracted from the ground before the mineral is separated from the rocks. The whole purpose of the process is to obtain pure gold from the rocks, but the gold-bearing rocks incorporate lots of different materials such as calcite, quartz, and sulfides of different metals ( Ilyas & Lee, 2018) . The process of gold production is intended to isolate the gold from everything else in the rock. The process of crushing gold-bearing is a particularly challenging, but necessary step. By crushing the gold-bearing rock, the surface areas through which mercury could act on the rock to form an amalgam with gold is increased.
The process does not simply imply application of brute force in hitting the rock with a sledge since pieces will fly all over the place and a portion of gold might be lost. For this reason, there is the need for an exceptionally solid compartment and hitting plate, an approach adopted in a bid to optimize the quantity of gold extracted from the gold-bearing rock. That way, the rock can be crushed without wasting any of the valuable particles of gold. There is also the need for an extraordinary sort of mallet, which fits into the holder without leaving any space for the rock to be thrown off the crushing areas.
Amalgamation and Distillation of Gold
In this process, mercury is used to get the gold out of the powdered rock. Like most minerals, gold dissolves in mercury to form a solution referred to as an amalgam, which is a physical mixture of mercury and gold and type of alloy. Amalgamation is a straightforward method of isolating the gold from the rock since the rock remains untouched by the mercury. In the amalgamation process, mercury is utilized to recover tiny bits of gold that are blended in silt and soil ( Coulson, 2012) . Mercury and gold settle and consolidate together to form an amalgam that can be easily separated from the rest of material. Thereafter, gold is extricated by vaporing the mercury. The vaporization of mercury is possible because of the differences in the boiling point of the two metals. The subsequent stage in the process is to isolate the gold amalgam from any 'unreacted' mercury. The crude amalgam is then forced through a chamois cowhide. Sparkling metallic bits of mercury overflow through the cowhide hence leaving the gold amalgam behind. The fact that mercury has a lower boiling point implies that it will evaporate first leaving gold.
The wetting of gold by mercury is certainly not a genuine alloying process. As the surface strain of mercury is more prominent than that of water, however, not as much as that of gold, it adsorbs onto the outside of gold particles. Also, since mercury exists as a thick medium, gold sinks into the mercury while the lighter gangue material floats overtop. At 20 o C, the dissolvability of gold in mercury is just 0.06%. In that regard, an assortment of amalgamation techniques are utilized in artisanal mining activities ( Lovitz, 2006) .
In another form of separating gold and mercury, gold dissolves in mercury in a manner similar to how salt breaks down in water. For this reason, miners submerge the gold in mercury, which would dissolve the gold but not other impurities. The mixture of mercury and gold would then be heated until the mercury vaporizes. Despite the fact that the gold would need to be refined later for the removal of more impurity, amalgamation with mercury allows effective extraction of gold from rocks and low-quality metals that are not as important as gold.
The production process involves obtaining gold amalgam and other advanced separation processes can be used to obtain pure gold from the amalgam. However, the challenge is to get gold, not some abnormal alloy ( Ilyas & Lee, 2018) . In that regard, this is where a potato proves to be useful. Mercury has a softening temperature well below that of gold, and, when gold amalgam is heated delicately, vaporization occurs to produce mercury fume and cleaned gold. The tissue of the potato absorbs the mercury vapor hindering it from escaping into the air or settling back into the vaporization chamber to form a gold-mercury amalgam.
Effects of Mercury in Mining
Although the extraction of gold is a lucrative economic activity, in some nations, the use of mercury in the mining process has been deemed too dangerous to engage in. Since the benefits are purported to outweigh the benefits, legislations barring the usage of mercury in gold mining have been ratified and implemented. The portrayal of mercury as a deleterious element has compelled researchers and experts in the mining industry to explore and develop alternative approaches for gold mining.
Principally, amalgamation saves up to 80% of the cost used to produce gold. Thusly, amalgamation reduces gold prices significantly as compared to other forms of gold production, such as panning and sluicing. However, the amalgamation of gold is a process that has dangerous outcomes to the environment and the health of animals and the human population ( Gibb & O'Leary, 2014) . The process leads to the vaporization of mercury that is emitted to the air, and some of it combines with water. Therefore, the process should be avoided or conducted with a lot of caution. Empirical researchers have proved that the usage of mercury in the extraction of gold results in ill-health both for animals and human beings. . The mercury vapor produced in the vaporization step of the amalgam may escape into the atmosphere, resulting in an increased prevalence of nervous, immune, and digestive system complications. According to the Worl Health Organization, exposure to mercury fumed can be fatal, depending on the longevity of exposure. The aforementioned ailments usually occur when an individual inhales, physically touches, or ingests the mercury residue.
In light of the health effects associated with the use of mercury in the mining process, entities such as the Global Environmental Facility have vehemently championed for the illegalization of the use of mercury and the ultimate arraignment of individuals that use the element in the extraction of gold ( Malm, 1998) . The motivation behind the urgency of banning the use of mercury stems from the fact that not only do more than 15 million gold miners from around the world work in somewhat dangerous conditions, the continued exposure to toxic chemicals such as mercury, further deteriorates the quality of their wellness.
In conclusion, although the extraction of gold from gold-bearing rocks can be efficiently undertaken using mercury, the process has been resented and illegalized in most countries. The usage of mercury in the mining of gold has been determined to cause digestive, immune, and nervous system complications. The bottom line is even though the use of mercury is economically beneficial, it should not be permitted as the effects of the endeavor on people is far-reaching.
References
Coulson, M. (2012). The history of mining: The events, technology and people involved in the industry that forged the modern world . Petersfield, UK: Harriman House.
Gibb, H. & O'Leary, K.G. (2014). Mercury Exposure and Health Impacts among Individuals in the Artisanal and Small-Scale Gold Mining Community: A Comprehensive Review . NLM-Export.
Ilyas, S., & Lee, J. (2018). Gold Metallurgy and the Environment . Boca Raton, FL: CRC Press.
Lovitz, S. B. (2006). Scales of responsible gold mining: Overcoming barriers to cleaner artisanal mining in southern Ecuador . M.S. University of Vermont .
Malm, O. (1998). Gold mining as a source of mercury exposure in the Brazilian Amazon. Environmental research , 77 (2), 73-78.
