Science and technology are closely related in the gold mining process. Especially in the extracting and processing of the metal. Gold is a golden yellow metal, which is solid at room temperature. Au is the symbol for gold, its atomic number is 79 and it is a transition element. Gold is a very soft metal. It can be beaten into the thickness of 0.000013 cm and according to Microsoft Encarta 29 g can be drawn out to 100km long! In this report I am going to investigate how gold is extracted and processed, I will look into the technology used and how gold mining effects the environment. Extraction and Processing of Gold. Gold can be extracted in many ways. Gold panning is an old way to mine but according to www.keenengineering.com the gold pan is still used in 75% of all countries in the world. The science behind gold panning is simple. While you shake the pan, the gold being heavier the rest of the stones and dirt will sink to the bottom of the pan. While swirling the pan around in the water, the light material will be washed out of the pan, leaving the gold at the bottom. This Process relies on the weight of the gold. One of the most common modern mining methods is the Cyanide process; this is used at the Martha Mine. This process starts with the mining of the rock. Then the rock is crushed to a suitable size to travel on a conveyor belt to the factory. The rock is now ground up and lime is added as well as water and steel balls. We are now up to the leaching and adsorption stage of the extraction process, ground ore, water and a weak cyanide solution are put into steel leach tanks where the gold is dissolved. Then the mixture passes through six adsorption tanks which contain carbon granules. The carbon then absorbs the gold. This stage removes 93% of the gold. The mixture now passes through electro winning cells. This is where the gold is won onto steel cathodes. A cathode is a type of electrical conductor. Now bullions are produced. A Bullion is a bar of gold which is at least 99.5% pure gold.
Gold mines tend to have a huge impact on the environment. From digging out a huge pit, to disposing of the left over chemicals and tailing. If a gold mine isn’t managed properly it can have some very negative impacts on the environment. A common impact is when water used in the mining process is polluted with chemicals from the factory and then put back into rivers and streams. Cyanide used to extract gold can pollute the rivers and kill fish and other life. Other waste products can also have bad effects on water quality. The air around a gold mine can also easily be polluted. Dust from open mine pits can blow around into the community. Chemicals such as nitrogen oxide and sulphur oxide can be released when the gold Bullions are made. There are also all the left over rocks to be dealt with, in some mines these leftovers are just abandoned when the mines close. Reducing the Impact
It’s not all bad for the environment. Careful planning can stop any bad effects on the
environment. At the Martha Mine they have some good practices to help the
environment. Before they put the water back into the river they clean it to a quality
standard, this stops any negative impacts on the river life. Like the Golden Cross mine the Martha mine also plans to turn the old mining pit into a lake after it has finished mining at the site. At the completion of the mining all the equipment will be dismantled and removed. They will then fill up the pit with water to create a recreational lake, which could be use for rowing or sailing. The edge of the pit will be used to create a shallow edge to the lake. Plants and bushes will be planted all around the mining area. The waste disposal area where all the stones and tailings are dumped will be transformed into an area of pasture, plantings and pounds.
Golden Cross mine after rehabilitation.
Gold and science are very much related. Without science we wouldn’t
know what chemicals to use to extract the gold from the rocks, and we
wouldn’t have any of the machinery needed to mine gold. We also need
science to test the water quality and to clean the used water. Gold
extraction and processing is a complex process which has many impacts
on the environment. But mines work hard to ensure that they only make
minimal damage to the environment around them.
“Gold.” Microsoft Encarta 2006 [CD]. Microsoft Corporation, 2005.
Video- Mining at Martha’.
http://www.marthamine.co.nz/-copyright 2000 2007
Newmont Waihi Gold Limited.
http://www.open2.net- Copyright 2006 The Open
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Wikimedia Foundation, Inc. 2007.
http://www.newzealandmint.com- 2007 New Zealand Mint Ltd
www.ecofootage.com- Copyright 2005-2006 EcoIQ
http://www.nodirtygold.org- Copyright 2004 Earthworks/Oxfam America