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Part Five, Issue 16

Part Five, Issue 16. Gold Mining: Is It Sustainable. Objectives. After reading the assigned chapter and reviewing the materials presented the students will be able to understand: What are mineral deposits? What are the environmental impacts of gold mining?. What is a mineral deposit?.

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Part Five, Issue 16

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  1. Part Five, Issue 16 Gold Mining: Is It Sustainable

  2. Objectives After reading the assigned chapter and reviewing the materials presented the students will be able to understand: • What are mineral deposits? • What are the environmental impacts of gold mining?

  3. What is a mineral deposit? • The term mineral deposit refers to economically valuable mineral assemblages that can be extracted and refined for profit. • Iron makes up nearly 6% of the earth’s crust, but must be concentrated up to about 50% to be economically viable. • The concentration at which the deposits become economically viable depend on the price of the commodity, the efficiency of the extracting process, subsidies, and cost of mitigating environmental impact.

  4. How do we use minerals? • The U.S. Geological Survey publishes an annual Minerals Yearbook tracking the production and use of nearly ninety mineral commodities (http://minerals.usgs.gov/minerals/). • Steel has been manufactured by alloying various metals with iron.

  5. Gold and Gold Mining • Half the gold ever produced on Earth has been produced since 1960. • The World Gold Council reports that the electronics industry is the world’s third largest user of gold, after jewelry and coins. • Gold is being increasingly incorporated into e-waste as a result of being used in electronics equipment.

  6. Modern Methods of Gold Mining • Cyanide is widely used in gold mining. It is one of the rare reagents that will dissolve gold in oxygenated water. Cyanide is extremely toxic. • Mercury is also used in gold mining. Methyl mercury is extremely toxic.

  7. Gold Mining by Cyanide Leaching • Cyanide leaching uses cyanide solutions to recover gold from huge piles of crushed low grade ore. Millions of tons of rock are crushed to yield profitable quantities of gold. • Gold mines collect cyanide laced wastewater in huge holding ponds, some of which can cover 60 acres. If these ponds fail an ecological disaster will likely result. • On Jan 30, 200 it happened in Romania. The waste contained 50 to 100 tons of cyanide. Hungary alone reported 1200 tons of dead fish. The discharge reached the river Danube and finally the Black Sea. It contaminated the drinking water of 2.5 million people. It has been called Europe’s worst natural disaster after Chernobyl (1986).

  8. Gold Mining with Mercury: The Amalgamation Method • Amalgamation is the alloying and collection of gold from ore using droplets or coatings of mercury. • Crushed gold ore is passed over surfaces coated with mercury, to which the gold binds. The mercury, precious metal amalgam is then collected and heated to vaporize and separate the precious metals. • Studies report fish in the Amazon river to be contaminated with mercury.

  9. Summary • The term mineral deposit refers to economically valuable mineral assemblages that can be extracted and refined for profit. • The concentration at which the deposits become economically viable depend on the price of the commodity, the efficiency of the extracting process, subsidies, and cost of mitigating environmental impact. • The World Gold Council reports that the electronics industry is the world’s third largest user of gold, after jewelry and coins. • Gold mines collect cyanide laced wastewater in huge holding ponds, some of which can cover 60 acres. If these ponds fail an ecological disaster will likely result. • Amalgamation is the alloying and collection of gold from ore using droplets or coatings of mercury.

  10. Home Work • 1. At what concentration does a mineral deposit become economically viable to mine? • 2. What are the 3 main uses for gold?

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