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Mining removes rocks and minerals that contain useful metals from the Earth’s crust.

Mining removes rocks and minerals that contain useful metals from the Earth’s crust. Image: G. Plumlee, USGS. Metals-2-1. The Mining Cycle. Exploration. Reclamation. Mining. Images: Martin Miller. Metals-6-1. Useful metals come from rocks and minerals in the Earth’s crust.

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Mining removes rocks and minerals that contain useful metals from the Earth’s crust.

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  1. Mining removes rocks and minerals that contain useful metals from the Earth’s crust. Image: G. Plumlee, USGS Metals-2-1

  2. The Mining Cycle Exploration Reclamation Mining Images: Martin Miller Metals-6-1

  3. Useful metals come from rocks and minerals in the Earth’s crust. Galena sample – a main ore of lead. Image: Stonetrust, Inc. Metals-6-2

  4. Geologists explore for useful metals by mapping, drilling, and sampling rocks and minerals. Image: Martin Miller Metals-6-3

  5. Many mines are large surface excavations. Image: Kennecott Utah Copper Co. Metals-2-2

  6. Some mines are underground. Image: US Bureau of Mines Metals-2-3

  7. Explosions - or blasts - break metal-bearing rock into blocks and fragments. Image: US Bureau of Mines Metals-2-5

  8. Crushed metal-bearing rock - most pieces smaller than a baseball - is ready for processing that removes metals. Image: Kennecott Utah Copper Co. Metals-2-7

  9. Separating metal-bearing minerals from others produces waste called “tailings”. Image: Kennecott Utah Copper Co. Metals-1-3

  10. Facilities called smelters melt metal-bearing minerals in ways that separate the metals from impurities. Image: Martin Miller Metals-3-7

  11. Historically, mineral processing to recover metals from minerals emitted large amounts of harmful gases and particles from smelters to the atmosphere. Image: Atlantic Richfield Company Metals-1-7

  12. Modern facilities to recover metals from minerals use new technology that reduces emissions below those permitted by regulatory agencies. Discharges at Kennecott smelter in Utah. Comparison units in metric tonnes. Acid Mist – 151 Acid Mist – 48 Particulates – 728 Particulates – 400 SO2 - 20,050 SO2 – 982 1992 Modernized (Permitted) Smelter Image: Kennecott Utah Copper Co., DeAtley Design Metals-1-8

  13. The molten metal recovered at smelters is poured into molds and allowed to solidify. This metal is then ready for refining and fabrication into things we need. Image: Martin Miller Metals-3-8

  14. Protecting against acid rock drainage is important at mines where sulfide minerals are present. Image: G. Plumlee, USGS Metals-4-1

  15. Rocks that contain useful metals commonly contain sulfide minerals - minerals that combine metal with sulfur. Image: Travis Hudson Sulfide minerals in a rock sample Metals-7-2

  16. The most common sulfide mineral is pyrite - or “Fool’s Gold” - a combination of iron and sulfur. Image: R. Busch Metals-7-3

  17. Pyrite occurs widely in rocks including disseminations through this entire mountain. Image: G. Plumlee, USGS Metals-7-4

  18. When pyrite (iron sulfide) comes in contact with oxygen in air or water, it “oxidizes” and turns into rusty iron oxides and sulfuric acid. Certain bacteria make this process go faster. Image: Travis Hudson Metals-4-2

  19. Sulfuric acid from oxidation of pyrite causes nearby soil and water to be acidic (acid rock drainage) and can harm habitat. Image: Travis Hudson Metals-4-3

  20. Preventing oxygen from contacting pyrite prevents acid rock drainage. Oxygen Sulfuric Acid Pyrite Bacteria Images: USGS Metals-4-4

  21. Acid rock drainage occurs naturally and is an environmental concern where sulfide minerals are mined. There are several ways to control or prevent acid rock drainage at mines. Image: Travis Hudson Metals-7-7

  22. Covering pyrite-bearing rocks with specially designed soil layers inhibits infiltration of oxygen-bearing water and neutralizes acidic conditions. Revegetated Pile Surface 12” Soil Growth Medium Uncompacted Lime-amended wasterock 12” Compacted consolidated wasterock Image: Kennecott Utah Copper Mine Metals-4-5

  23. In some cases, treatment plants add lime and other chemicals to acid rock drainage that neutralize the acidic waters and help remove dissolved metals. Image: Atlantic Richfield Company Metals-4-7

  24. Constructed wetlands can remove dissolved metals from certain types of acid rock drainage and prevent continued oxidation of pyrite or other sulfide minerals. Before After Images: ASARCO, Inc. Metals-4-6

  25. All mines eventually deplete their valuable metal-bearing rock and close. Image: Kennecott Utah Copper Co. Metals-2-8

  26. After mining removes the rocks containing useful metals, surface disturbances are covered with soil layers and revegetated. This is called reclamation. Image: Kennecott Utah Copper Co. Metals-6-6

  27. Recycling of used materials is another important source of metals. Recycled Metal Percentage Supplied Iron and Steel 45% Copper 43% Aluminum 32% Lead 55% Zinc 19% Stainless Steel 50% Metals-5-3

  28. Recycling of metals takes less energy than processing metal-bearing rocks. Recycled Metal Energy Savings Aluminum 95% Copper 85% Iron and Steel 74% Lead 65% Zinc 60% Metals-5-4

  29. Recycling of metals conserves our natural resources. Image: EPA Metals-5-5

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