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