An ore is an economically
exploitable deposit
North Carolina's official state precious stone is the emerald.
North Carolina's official state rock is granite. North Carolina leads the nation in the production of
feldspar, mica and pyrophyllite. Mining is a half-billion dollar industry in North Carolina. The largest emerald crystal ever found in North America
came from North Carolina. North Carolina is divided into three physiographic
provinces: Blue Ridge, Piedmont and Coastal Plain. North Carolina's geology represents more than a billion
years of constant change.
Average Concentration of Average Concentration of Valuable Metals in the CrustValuable Metals in the Crust
AluminumAluminum ~8% ~8% IronIron ~5% most Fe and Al is in silicate ~5% most Fe and Al is in silicate mineralsminerals and is not used as an ore and is not used as an ore TitaniumTitanium 0.44% 0.44% NickelNickel 75 ppm or 0.0075% 75 ppm or 0.0075% ZincZinc 70 ppm or 0.0070% ppm 70 ppm or 0.0070% ppm = = CopperCopper 55 ppm 0.0055% parts 55 ppm 0.0055% parts per millionper millionLeadLead 13 ppm or 0.0013% 13 ppm or 0.0013% SilverSilver 0.07 ppm 0.07 ppm GoldGold 0.004 ppm 0.004 ppm
Worthless minerals that are associated with the valuable minerals in an ore
Concentrating and smelting removes as much of this gangue as possible
Acid Mine Acid Mine DrainageDrainage
Coeur D' Alene Mine in Coeur D' Alene Mine in ColoradoColorado
Form as a result of natural processes concentrating an element(s) Hydrothermal and Precipitation Gravity Settling and Filter Press Metamorphic fluids Placer Deposits Secondary Enrichment
Refers to “hot water” Heat from magma, unusually
hot rocks, or metamorphism May reach 500-700 C Hot fluids are much better
solvents than cold
Saturated solution – as much material is dissolved as it can hold
Cooling of saturated solution leads to supersaturation
Dissolved metal comes out of solution as a solid – process is called precipitation
Rain occurs when vapor turns to liquid
A large quartz boulder with a lot of visible gold. Usually, the gold is much finer and hard to see.
Solids sink to bottom of liquid
Weight squeezes fluid out
Metamorphism may generate hot fluids
These fluids, with dissolved ions in them, move through rock, altering it
Weathering and erosion often remove soft easily abraded minerals, leaving a concentrated ore behind
Dissolution and reprecipitation can also produce an ore
What is an economic geological resource? A mineral that is heavily used in some
human endeavor (e.g., metal ores) and therefore is an important part of domestic/international commerce.
What are some mineral resources that are economically important? metals. examples? non-metal resources. examples?
What makes something into an economic resource?
Are we running out of mineral resources? How would you find this out? What do you need to know?? Total discovered stocks likely (but undiscovered) resources speculative resources
Source: Miller, G. Tyler, Living In The Environment. (2000) Wadsworth Publishing. New York.
US Non-renewable Resource US Non-renewable Resource ReservesReserves
Source: Miller, G. Tyler, Living In The Environment. (2000) Wadsworth Publishing. New York.
1. Prospecting: finding places where ores occur
2. Mine exploration and development: learn whether ore
can be extracted economically3. Mining: extract ore from ground4. Beneficiation: separate ore minerals from
other mined rock5. Smelting and refining: extract pure
commodity from the ore mineral6. Transporation: carry commodity to market7. Marketing and Sales: Find buyers and sell
the commodity
The decision to mine (or not to mine) a particular ore deposit depends upon:
1. an analysis of costs, benefits and risks
2. tangible (i.e. dollar profit)
3. intangible (i.e. hopes of stimulating the economy, fears of environmental damage)
Important Factors: 1. Applying knowledge of association of ores with
specific geological settings. 2. Using remote sensing techniques such as satellite
imagery, seismic reflection profiles, magnetic field intensity, strength of gravity to detect geological structures. • Photos useful in finding faults. • Small basaltic intrusions have prominent
magnetic anomalies. • Dense ore bodies can have prominent gravity
anomaly. 3. Developing detailed maps of rock types and
geological structures (faults, folds, intrusions). 4. Developing 3-d picture of geological structures
containing ore. 5. Obtaining samples of ore for chemical analysis.
1.Define size, shape and grade of ore body. • Grade, G: mass of commodity per mass
of ore• Gold: 5 grams of Au per metric ton (106
grams of ore) Grade = 5 x 10-6. • Aluminum: 400 kg of Al per metric ton
of ore, G=0.4. 2. Drill cores, though expensive, can be
used to determine underground extent of ore
3. Estimate the mass of the commodity:(mass of commodity = volume of core body x density of ore body
x grade)
Mine Exploration and Development: Learn Whether Ore can be Extracted
Economically
4.Design a profitable plan for mining.
•Selecting appropriate mining techniques are just a small part of it!
•Analysis of requirements to startup mine: capital, transportation, labor, etc.
•Complying with governmental regulations.
•Mitigating environmental damage. •Strategies for making profitability in
a changing marketplace.
Types of Mining: • Surface Mining: Scoop ore off surface or earth.
• cheap. • safe for miners. • large environmental destruction.
• Underground Mining: Use of shafts to reach deeply buried ores.
• expensive. • hazardous for miners. • less environmental damage.
Gradual shift toward surface mining
Surface mining
Used with widespread, evenly distributed minerals
Used for copper, iron, gold, diamonds, coal, clay
Quarries: open pits for clay, gravel, sand, stone (limestone, granite, marble, slate)
Huge amounts of waste rock are removed to obtain small amounts of minerals. One Utah mine is 4 km (2.5 mi) across
and 1.2 km (0.75 mi) deep.
Surface Surface MiningMining Open Pit mining:
• circular hole in ground, with ramp circling down along sides, allows deeper ore to be reached.
Layers of surface soil and rock are removed to expose the mineral resource.
Overburden: overlying soil and rock that is removed by heavy machinery After resource extraction,
each strip is refilled with the overburden.
Used for coal, sand, gravel, and oil sands
Acid drainage: sulfuric acid forms and flows into waterways
http://www.youtube.com/watch?v=O3fwVpoQW98
Strip Strip MiningMining strip-mining:
scoop off rock overburden, and then scoop off ore material.
• Economics of strip mining depend on stripping ratio
• Large land area can be involved, especially for coal and bauxite.
Economics of strip mining depend on stripping ratio
stripping ratio = h1/h2
Accessing deep concentrations of a mineral through tunnels and shafts
Used for zinc, lead, nickel, tin, gold, copper, diamonds, phosphate, salt, coal
The most dangerous form of mining Injury and death from
dynamite blasts and collapsed tunnels
Toxic fumes and coal dust can be fatal
Acid drainage and polluted groundwater
Underground MiningUnderground Mining• A technology originating in antiquity. • A variety of configurations, depending upon conditions
Panning for gold in a placer deposit
Using running water, miners sift through material in modern or ancient riverbeds. Congo’s coltan
miners, California’s gold rush of 1849
Used for gold, gems
http://www.youtube.com/watch?v=ucX2fkLPMqE
Entire mountaintops are blasted off and the waste is dumped into valleys.
Mainly for coal in the Appalachian Mountains
Economically efficient Deforestation, degrades
and destroys vast areas, pollutes waterways, erosion, mudslides, flash floods
http://www.youtube.com/watch?v=hgGSUfpJcOQ
Mine blasting cracks foundations and walls. Floods and rock slides affect properties. Overloaded coal trucks speed down rural roads. Coal dust causes illness. High efficiency mining reduces the need for
workers.
The "diamond crawl" in a deflation basin, Diamond Area No 1, Namibia
Diamond concentrations were increased by wind erosion
Mining Mining IssuesIssues Mine Safety: In U.S., stringent mining regulations have lead to a reduction in fatalities, both in terms of total deaths per year, deaths per person-hour worked, and deaths per ton mined.
surfac
e
It encourages mining on federal lands by letting any U.S. citizen stake a claim on any public land for a few dollars per acre.
The public gets no compensation for any minerals found.
Once a person owns the land, that land can be developed for any reason, having nothing to do with mining.
Health ProblemsHealth 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 DamageEnvironmental Damage• Gaping holes in ground (old open pit
mines). • Piles of mine tailings (non-ore removed
from mines). • Accidental draining of rivers and lakes. • Disruption of ground water flow patterns. • Loss of topsoil in strip-mined regions (350
to 2,700 km2 in US alone). • Contamination from sulfuric acid (H2SO4)
produced through weathering of iron sulfide (FeS2, pyrite) in tailings.
4FeS2 + 14H2O = 4Fe(OH)3 + 8H2SO4
• Contamination from heavy metals (e.g. arsenic, mercury) in mine tailings.
What is a mineral? naturally occurring, inorganic, solid
element or compound with a definite chemical composition and a regular internal crystal structure
What is rock? solid, cohesive, aggregate of one or
more minerals Each rock type has a characteristic
mixture of minerals
Alloy: a substance formed by mixing, melting, and fusing minerals (i.e., steel = iron + carbon)
Smelting: removes metal from ore using heat and chemicals Melting and reprocessing the metal produces
the strength, malleability, or other characteristics desired.
Processing minerals impacts the environment. Water and energy intensive Toxic air pollution Tailings: heavy metals and chemicals in the
ore left after the metal has been extracted
Beneficiation: Separate Ore Beneficiation: Separate Ore Minerals from other Mined RockMinerals from other Mined Rock
• Ore rarely contains enough ore minerals to be refined as is. • Milling required to separate pure ore minerals from useless
"gangue" minerals. • Milling techniques.
• Grinding ore to fine powder. • Separation using flotation techniques:
• powdered ores mixed with water and organic "collector" and "frother" compounds
• collector are heteropolar molecule with one end that adheres to ore minerals
• the other that adheres to frother coated air bubbles• Air forced through water then produces a foamy layer
of concentrated ore mineral. • Environmental problems associated with mill tailings are
similar to mine tailings.
Smelting and Refining: Extract Pure Commodity from Ore Mineral
• Iron, from an iron oxide (Fe2O3, 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.
1. Production of huge piles of slag. 2. Emission of CO2, 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.
Smelting and Refining: Smelting and Refining: Environmental ProblemsEnvironmental Problems
Cost of ProductionCost of Production•Costs that scale with grade of ore. The lower the
grade, • The more ore must be mined. • The more ore must be shipped to the mill. • The more ore must be milled. • The more tailings must be disposed of..
•Fixed costs. • Building a transportation infrastructure. • Refining ore minerals, once it has been milled.
•Cost formula.cost of producing a kg of commodity =cost of producing a pound of ore / grade of ore+ fixed costs per kg of commodity
• Amount of commodities mined per year has generally increased.
• Commodity prices can take big swings, but average prices during the last century often declined or remained constant.
Cost TrendsCost Trends
Ore grades have all decreased as milling technology has improved
copper
Cents per pound
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