Mining. Mining: the extraction of valuable minerals or other geological materials from the Earth

Transcription

1 Mining Mining: the extraction of valuable minerals or other geological materials from the Earth Ore: rocks that contain high concentrations of metals/minerals 1

2 Categories of Mineral Resources: energy resources: coal, oil, natural gas, uranium metallic mineral resources: iron, copper, aluminum, etc nonmetallic resources: salt, gypsum, clay, sand, phosphates, water, & soil. If it isn't made of wood, cloth, or other living matter, it was dug out of the ground. 2

3 To maintain our standard of living, each person in the United States requires over 48,000 pounds of minerals each year: * 12,428 lb. of stone * 9,632 lb. of sand and gravel * 940 lb. of cement * 276 lb. of clays * 400 lb. of salt * 302 lb. phosphate rock * 425 lb. of iron ore * 77 lb. of bauxite (aluminum) * 17 lb. of copper * 11 lb. of lead * 10 lb. of zinc * 6 lb. of manganese Note: these amounts are refined final products: they do not include waste material *.0285 T oz. gold * 29 lb. of other metals Plus: * 7,667 lb. petroleum * 7,589 lb. coal * 6,866 natural gas * 1/3 lb. uranium Online, the USGS (United States Geological Survey) quoted the Mineral Information Institute with these stats: Most mining (by weight) is for construction materials (e.g. stone, sand and gravel) Metals are mined in smaller quantities but are much more valuable. 3

4 Metal Mining Iron is the most mined followed by aluminum and copper Gold is mined in much smaller quantities, but is much more profitable. Metal Quantity y( (tons) Iron 845,000,000 (as steel) Aluminum 135,000,000 Copper 15,000,000 Gold 2, Data; State of the World

5 Introduction to Mining Supplies: Introduction to Mining Currently U.S. imports more than 50% of major non-fuel minerals Reserve deficiency for: silver, tungsten, sulfur, zinc, gold, potash. No reserves for: manganese, cobalt, tantalum, niobium, platinum, chromium, nickel, aluminum, tin, antimony, fluorine, asbestos, vanadium; 5

6 Reserves: Introduction to Mining Identified resources that can be extracted economically at current prices using current mining technology Energy to get the material Finding Extracting Ore needs to be refined and smelted Process differs depending on mineral Ore can travel thousands of miles to be processed 6

7 Extracting Mineral Resources Strip mining Open pit mining Subsurface mining Dredging 7

8 Strip mining Open Pit mining Kennecott Cu Mine, Utah Copper, gold, silver, molybdenum Tailings deposit Omai Mine Guyana 8

9 Gold ore not like this picture was like this in 1800 s now in most cases 0.05 oz/ton Copper ore- 4.5% of ore now is 0.4% Dredging Placer mining 9

10 Processing Smelting A high-temperature process that separates out a pure metal, usually in a molten form, from an ore Chemical extraction-cyanide heap leaching Pre-processing-autoclave/roaster Aluminum: requires a lot of electricity to process (requires constant temperatures of 980 C) >2% of all the world s electricity is used to produce aluminum. >25% of the world's aluminum production relies coal for electricity 10

11 Alcoa and aluminum videos How stuff works aluminum mining 11

12 Shipping Recycling 12

13 Introduction to Mining Iceland: Imports aluminum ore from Australia to process using geothermal electricity 13

14 Gold Use and Properties Properties of Gold: -nontoxic -efficient conductor of electricity -the most ductile/malleable of all metals -corrosion resistant (will not rust or tarnish) -high thermal reflectivity Gold Mining $906/oz in Jan Large increase in the price of gold Gold Price $/oz Year 14

15 History of gold mining is about Ore grade Technology Energy Demand-Population Gold Mining The modern gold rush 82% of gold mined in US is in Nevada Third in the world 15

16 Gold Mining Industrial large scale by corporations Small-scale (artisanal) by individuals Artisanal Gold Mining Artisanal Miners: people working with simple tools and equipment, usually in the informal sector, outside the legal and regulatory framework. The vast majority are very poor, exploiting marginal deposits in harsh and dangerous conditions and with large impact on the environment. 16

17 Artisanal Gold Mining An estimated 13 million people work as artisanal miners, spanning at least 30 countries in Latin America, Africa, and Asia, and contributing to the livelihoods of approximately million people. ~25% of the world s total gold output comes from artisanal mining Artisanal Gold Mining Environmental Impacts: Mercury is used to amalgamate the gold Lack of pollution control structures (tailings ponds): Cyanide contamination Suspended sediments Acid drainage Metals pollution 17

18 Artisanal Gold Mining Mining in the Brazilian Amazon Before Mining Upstream of mines After Mining Downstream of mines Mercury Use: Artisanal Gold Mining Mercury use for gold mining in the developing world has increased exponentially with increased demand for gold Why Mercury: Gold bonds to mercury, forming an amalgam that increases the density of gold, making the gold easier to collect from the rest of the sediment. 18

19 Large Scale Industrial Gold Mining Gold Mining 19

20 Gold Mining Mine Processes Holes drilled and ore examined for grade and metallurgical properties Blast rock Based on its metallurgical makeup, trucks deliver the ore to different processing locations Gold Mining Waste Rock/Overburden High grade ore Grinding Mill Low grade ore Carbonaceous Oxide Sulfide Heap Leach Pad Tailings al pond Gold Collected on Activated Carbon 20

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22 Environmental Impacts of Mining Land use Water use Fossil fuel emissions/energy use Cyanide use Mercury emissions Aid Acid mine drainage 22

23 Water Mine use Mine release Groundwater Environmental Impacts: Water Use Mine pits are often below the water table De-water the area around the mine The water removed from groundwater is: Used in heap leaches on the mine Used for agriculture Pumped into infiltrations ponds or rivers 23

24 Environmental Impacts: Acid Mine Drainage Acid Mind Drainage: low ph water (<5) laden with iron, sulfate and other metals Occurs when the rock contains sulfide minerals Sulfide reacts with oxygen and water to form sulfuric acid 2FeS (s) 7O 2 (g) 2H 2 O(l) 2Fe (aq) 4SO 4 (aq) + 4H + (aq) Environmental Impacts: Cyanide Cyanide is used to extract (leach) gold out of low-grade ore in heap leaches Developed in the late 1800s Environmental Impact: Wildlife deaths particularly birds 24

25 Environmental Impacts: Water Use Pit lakes Environmental Impacts: Energy 10% of the worlds energy is used in mining (WWI, 2003) Much of the energy used are fossil fuels. 5% of the world s total green house gas emissions are from fossil fuels (Baumert, K, Herzog, T and Pershing, J, 2005). 25

26 Environmental Impacts: Mercury Emissions Mineral trends high in gold are often naturally enriched in mercury Cinnabar (HgS) in rock from Nevada Point Source Emissions Hg Fugitive Hg Emissions 26

27 Surface Mining Control and Reclamation Act 1977 Coal mining-strip mines Requires coal companies to remove soil in layers when done return to original contour and vegetate Coal producers pay a 8% royalty U.S Mining Law Mining claim - $100/claim plus filing fee Patented claim-demonstrate full title, demonstrate a deposit, filing fee 27

28 U.S Mining Law Mining claim - $100/claim plus filing fee Patented claim-demonstrate full title, demonstrate a deposit, filing fee Your book-no provision for reclamation of damaged land (this is not true in Nevada.. State laws coverrequire bonding); environmentalists favor reform of law -patenting issue/royalties/stronger environmental requirements time to use up a certain proportion (usually 80%) of reserves extended by recycling, reuse, & reduction of consumption Depletion Time 28

29 Environmental Solutions/ Alternatives Reduction of material use Alternative sources of materials: --Landfill mining --Recycling Continue mining and mitigate/minimize environmental impacts: -- reclamation bonds -- emissions controls --etc 29