Mineral Resources
Resource:
Reserve:
Concentration Factor:
Strategic minerals: world industry depends on about 80 minerals, of these approximately 18 are scarce. A strategic mineral is a mineral that a country uses but is unable to produce itself.
Metals:
Malleable
conduct electricity
conduct heat and cold
tensile strength
Nonmetals:
Brittle
Do not conduct electricity
Do not conduct heat/cold
No tensile strength
Mineral Deposits: a variety of geochemical and geologic processes have acted to concentrate mineral resources in deposits that can be mined economically.
Igneous Deposits: many mineral deposits are associated with various igneous deposits.
Divergent Plate Boundaries: cold water flowing into fractures is heated by the magma source and leaches out minerals from surrounding rock concentrating them into veins. Metal oxides and sulfides
Convergent Plate Boundaries: partial melting of seawater saturated rocks extracts and concentrates minerals. Iron, copper, gold, zinc, lead
Magma chambers: hydrothermal solutions flowing through rocks leach minerals and concentrate them into veins. Iron, copper, zinc, gold, silver, platinum, uranium
Sedimentary Deposits:
Banded Iron Formations: ancient sedimentary deposits rich in iron.
Evaporite Deposits: evaporating mineral rich water deposits a variety of salts.
Placer Deposits: minerals weathered and eroded from rocks are concentrated in sand and gravel deposits according to density by running water.
Laterites: heavily weathered soils, most known for rich aluminum ores (bauxite).
Seawater Precipitates: manganese nodules and phosphate nodules are formed on the ocean floor from the precipitation of minerals out of seawater. Phosphate nodules found in shallow water, manganese in deep water.
Examples of mineral resources:
Iron: very abundant in the crust, ore usually obtained from ancient sedimentary deposits.
Aluminum: obtained from bauxite, a weathered soil deposit. VERY energy intensive to produce. 3-4% of all US energy is used in the production of aluminum. Much easier and less energy intensive to recycle.
Metals: including gold, silver, copper, lead, zinc and others associated with sulfide deposits formed from hydrothermal activity.
Nonmetals: salts from evaporite deposits, sands and gravels, sulfur from volcanic activity
Mineral production and processing:
Mining: mining techniques depend upon the mineral and the geologic setting.
Underground Mining: discussed with coal. Environmental impact the same. Mine drainage acidic.
Strip Mining: discussed with coal. Environmental impact the same.
Open Pit Mine: very similar to strip mine. Mineral resource recovered by digging open pit. The deeper the resource is located the wider the pit at the surface. Environmental impact the same as strip mining. Bingham Mine, Utah: largest open pit mine in the world. Since 1906 3.3 billion tons of material has been removed from mine. 15% of all US copper comes from this mine.
Solution Mining: inject solvents under the ground to extract mineral resource. There is the concern with the solution leaking into the groundwater. This method also produces a large amount of liquid waste that is often toxic.
Ore Processing: the ore is crushed and then the mineral must be removed from the host rock.
Crushing: produces large amounts of dust. Much of this has high sulfur contents and can produce acid deposition down wind.
Separation: solvents are used to separate the mineral from the ore. These solvents are usually hazardous, toxic material. Large amounts of liquid waste are produced. Example of solvents: mercury, cyanide
Tailings Piles: One of the largest forms of waste from the processing of ore. These piles consist of crushed waste rock. Often high in sulfur, runoff flowing through these piles can be VERY acidic. This acidity releases metals to a soluble form and causes nutrient elements to become less available.
New environmental attitudes and legislation has made the mining process more environmentally friendly. Runoff from tailings piles dammed and collected and treated. Dust is reduced. Biotechnology uses bacterial organisms to degrade solvents used in the separation process.
Case Study: Homestake Gold Mine
Wetlands are created adjacent to mines to collect and filter watses.
The PROBLEM is that thousands of abandoned mines throughout the West continually release very acidic water to the environment. Tailings piles that have been abandoned also contribute to the metal pollution of streams and lakes in these areas.
1977 Surface Mining Control and Reclamation Act: requires restoration of land to its original contour. Aimed at coal mining only, it does not address mineral extraction. It adds 50% to the cost of mining.
