Minerals and Mining
What are minerals? A mineral is defined as any naturally occurring crystalline inorganic material. The internal structure of a mineral is also important. Its chemicals and how they are arranged makes a difference. Some are composed of one element (Gold) A single item off of the periodic table Most mineral are compounds they consist of two or more elements that are combined in constant proportions. Some are mixtures Multiple compounds where you can see the different compounds ( layers, colors, or shapes) - Rocks
Element, Compound, or Mixture Copper Cu Element Minerals Pyrite FeS 2 Iron Sulfate Compound Granite - Minerals are mostly quartz and feldspar, with small amounts of mica (muscovite or biotite). Igneous Rock
Minerals There are over 2000 kinds of minerals, Which one s are worth looking at? Almost any rock you find will contain one or more minerals. Some are very rare and valuable
Mineral Properties Color Crystal form Hardness Cleavage Streak Luster Density Solubility Physical Physical Physical Physical Physical Physical Chemical Chemical
Density Density = Mass / volume The structure is highly ordered and constant for that mineral A grain of salt has the same structure as a boulder of salt.
General Classification of Nonrenewable Mineral Resources The U.S. Geological Survey classifies mineral resources into four major categories: Identified: known location, quantity, and quality or existence known based on direct evidence and measurements. Undiscovered: potential supplies that are assumed to exist. Reserves: identified resources that can be extracted profitably. Other: undiscovered or identified resources not classified as reserves
General Classification of Nonrenewable Mineral Resources Examples are: fossil fuels coal, oil metallic minerals copper, iron nonmetallic minerals sand, gravel Figure 15-7
ENVIRONMENTAL EFFECTS OF USING MINERAL RESOURCES The extraction, processing, and use of mineral resources has a large environmental impact. Figure 15-9
Minerals In a cycle that spans tens on millions of years, tectonic plates shift, grind, and recycle earth minerals in many ways. Once minerals are uplifted to the surface, they undergo weathering. These plate interaction locations have the greatest concentration of minerals.
Minerals There are 92 naturally occurring elements on earth but only eight elements make over 98% of the minerals on the Earth's crust. They are, in decreasing quantity, 1 oxygen 5 calcium 2 silicon 6 sodium 3 aluminum 7 potassium 4 iron 8 magnesium There are over 2000 minerals on Earth, but only 100 are commonly found. 30 minerals make up the majority of the rocks on Earth. Rocks are made of two or more of these minerals.
Ore Ore is any material that can be mined for a profit. Metal or nonmetal. Periodic Table Metals are the left side of the periodic table. Non-metals the right side of the table.
Ore Ore bodies are deposits or accumulations of ore in a mass of rock. Non-renewable The price determines the potential profit vs. amount found.
Steps in Obtaining Mineral Commodities 1. Prospecting: finding places where ores occur 2. Mine exploration and development: learn whether ore can be extracted economically 3. Mining: extract ore from ground 4. Beneficiation: separate ore minerals from other mined rock 5. Smelting and refining: extract pure commodity from the ore mineral 6. Transporation: carry commodity to market 7. Marketing and Sales: Find buyers and sell the commodity
Mining and the Environment Mining has an impact because minerals are removed from the earth by underground or surface excavations. The impact depends on the land, the water, the depth of mineral, the amount removed, method used, soil type, and surrounding rock. It can also effect the atmosphere. The amount of dust produced, the refining process. It can effect the water, by having runoff carry the pollutants uncovered.
ENVIRONMENTAL EFFECTS OF USING MINERAL RESOURCES Minerals are removed through a variety of methods that vary widely in their costs, safety factors, and levels of environmental harm. A variety of methods are used based on mineral depth. Surface mining: shallow deposits are removed. Subsurface mining: deep deposits are removed.
Surface mining low tech Panning for gold (Placer deposition) Diamond crawl (Aeolian placer)
Surface Mining Scoop ore off surface of earth. cheap. safe for miners. large environmental destruction.
Open-pit Mining Toxic groundwater can accumulate at the bottom. Circular hole in ground, with ramp circling down along sides, allows deeper ore to be reached Machines dig holes and remove ores, sand, gravel, and stone. Figure 15-
Bingham Canyon Mine
Figure 15- Area Strip Mining Earth movers strips away overburden, and giant shovels removes mineral deposit. Often leaves highly erodible hills of rubble called spoil banks.
Surface Strip mine
Potash Mining in Aurora, NC
Figure 15- Contour Strip Mining Used on hilly or mountainous terrain. Unless the land is restored, a wall of dirt is left in front of a highly erodible bank called a highwall.
Contour Strip Mining
Economics of strip mining depend on stripping ratio stripping ratio = h 1 /h 2
The faster we can dig, the more money we can make.
Mountaintop Removal Machinery removes the tops of mountains to expose coal. The resulting waste rock and dirt are dumped into the streams and valleys below.
Subsurface Mining Use of shafts to reach deeply buried ores. expensive. hazardous for miners. less environmental damage.
Health Problems collapse of mine. fire (methane, coal dust, etc.). asphyxiation (methane, carbon monoxide, etc.). pneumoconiosis (from inhaling coal dust). asbestosis (from inhaling asbestos fibers). silicosis (from inhaling silicate dust). heavy metal poisoning (e.g. mercury). radiation exposure (in uranium mining).
Environmental Damage Gaping holes in ground (old open pit mines). Piles of mine tailings (non-ore removed from mines). Contamination from heavy metals (e.g. arsenic, mercury) in mine tailings. Accidental draining of rivers and lakes. Disruption of ground water flow patterns. Loss of topsoil in strip-mined regions (350 to 2,700 km 2 in US alone).
Environmental Damage Contamination from sulfuric acid (H 2 SO 4 ) produced through weathering of iron sulfide (FeS 2, pyrite) in tailings. 4FeS 2 + 14H 2 O = 4Fe(OH) 3 + 8H 2 SO 4 Subsidence from subsurface mining
Figure 15- Mining Impacts Metal ores are smelted or treated with (potentially toxic) chemicals to extract the desired metal.
Acid Mine Drainage the outflow of acidic water from (usually abandoned) metal mines or coal mines Tailings piles or ponds may be a source of AMD.
Acid Mine Prevention the waste rock and tailings from a mine must be prevented from contacting oxygen Prevention is best since mine drainage can have long lasting effects.
AMD remediation Lime Neutralization Most common method Lime is added to increase ph to ~9 to cause precipitation of heavy metals Other methods include: Calcium silicate neutralization Carbonate neutralization (limestone chips) Constructed wetlands (after limestone neutralization)
Smelting and Refining: Extract Pure Commodity from Ore Mineral Iron, from an iron oxide (Fe 2 O 3, hematite) rich ore (such as a banded-iron formation, which also contains quartz). Coke (carbon from coal), ore, air, and limestone mixed in blast furnace.
Smelting and Refining: Environmental Problems 1. Production of huge piles of slag. 2. Emission of CO 2, a greenhouse gas, into the atmosphere. 3. Pollution associated with the generation of electricity needed in anode furnaces (especially aluminum). 4. Sulfur dioxide emissions from the refining of sulfide ores are a major source of air pollution. The sulfur dioxide combines with water to produce sulfuric acid. 5. Release of heavy metals (As, Cd, Hg), present in trace quantities in sulfide ores, into the atmosphere.
Air pollution Smelting Plant H 2 O discharge Toxic waste products
Mining Legislation Mining Law of 1872 allowed for the recovery of ores or fuels from federal lands. Encouraged development and settlement of the west Surface Mining Control and Reclamation Act of 1977 regulates surface mining of coal and the surface effects of subsurface coal mining Requires minimum disturbance during mining and reclamation after mining is complete.
Reclamation Reclamation time varies with the resilience of the ecosystem.
Reclamation Re-contour/Re-grade the land Return topsoil Replant appropriate plants (natives that foster succession) Purpose is to make the soil physically stable (minimal erosion, water infiltration/retention returns to normal)
How to reduce environmental impact Very strict governmental rules? Taxes money helps reclaim land Switch to different minerals REDUCE, REUSE, & RECYCLE