Formation and Extraction Ontology

Desawi Yosef

Geol – 4123 _E-1

Gold

Gold is one of the oldest mined and highly valued rare minerals in the world. According to the big bang theory, every element comes from the series of explosions of an initially packed small point some 13.7 billion years ago, and gold, like any other element was formed from this process. All the gold deposits around the world are produced during this time and process, and distributed everywhere; some in huge chunks and near the earth’s surface like in South Africa’s Witwatersrand basin, the world’s largest known gold reserve, and others scattered almost everywhere in rivers, oceans, hard rocks etc. on the surface or deep inside the earth’s crust making them impossible or economically infeasible to extract. So, gold is found almost everywhere and only its accessibility is what makes some countries the buyers while very few are the major producers who generate billions of income and employment to their respective citizens.

Gold mining techniques can be grouped into two: as small and large scale mining methods. Small scale mining depends on placer deposits, sediments transported from the country’s countless mountains downhill through weathering, erosion, gravity and streams. Small scale uses mining methods like gold panning, metal detectors and others. As soil is removed by erosion, gold gets exposed and available for prospecting.

Other gold extracting methods include amalgamation and cyanidation which uses chemicals, and can be used in medium to large scale commercial mining. Large scale techniques like pit mining and underground mining usually involves digging deep into the ground.. Sediments extracted from the ground are then processed using chemicals like cyanide to separate the gold from the rocks. Once the ore is brought to the surface, it’s crushed into smaller sizes before the chemical is added to it. Sodium cyanide is typically the largest single operating cost in the gold processing plant in this mining technique. Most plants simply allow the natural degradation processes of volatilization, complex breakdown by solar ultraviolet radiation, precipitation and oxidation to occur in the tailings storage facility. To extract gold from low grade ores, heap leaching is practiced, where the huge heaps are sprayed with a solution of sodium cyanide to dissolve the gold. When gold dissolution is complete, the ore-bearing solution is separated from the solids. Finally, the gold is separated from the bond by applying other chemicals. Application of ozonation treatment to thiocyanate-bearing liquors are commonly present in bacterial oxidation plants, and would warrant consideration for inclusion on the recycle or bleed streams.

Minerals are great resources to transform a country’s economy, but the process to extract them out of the ground could have a devastating effect on the environment and communities near the mining place. Small or large, on both categories, huge amount of sediments are displaced and processed usually using chemicals like mercury and cyanide to separate the gold from the rocks. The chemicals released from these processing plants are a source of surface and ground water pollution that could result in serious ecological disasters, sometimes persisting and affecting generations unborn.