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 Valuable Metals in the Crust Aluminum ~8% Iron ~5% most Fe and Al is in silicate minerals and is not used as an ore and is not used as an ore Titanium 0.44% Nickel 75 ppm or % Zinc 70 ppm or % ppm = Copper 55 ppm % parts per million Lead 13 ppm or % Silver 0.07 ppm Gold 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 Drainage

Coeur D' Alene Mine in Colorado

 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 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 Reserves 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 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

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 (10 6 grams of ore) Grade = 5 x Aluminum: 400 kg of Al per metric ton of ore, G= 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 Mining 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 O3fwVpoQW98

Strip Mining 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 = h 1 /h 2

 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 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 fkLPMqE

 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 GSUfpJcOQ

 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 Issues 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. surface

 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 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). 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). Contamination from sulfuric acid (H 2 SO 4 ) produced through weathering of iron sulfide (FeS 2, pyrite) in tailings. 4FeS H 2 O = 4Fe(OH) 3 + 8H 2 SO 4 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 Minerals 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 (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.

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. Smelting and Refining: Environmental Problems

Cost 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 Trends Ore grades have all decreased as milling technology has improved copper Cents per pound