Mineral Resources & Mining

Eight chemical elements make up 98.3% of Earth’s crust. Oxygen Silicon Aluminum Iron Calcium Sodium Magnesium Potassium

Other elements comprise 1.7% of Earth’s Crust Many of these are important to industry Distribution of these elements is not uniform across the Earth. Examples: Ni, Ti, Cr, Cu, Pb, Zn, U, Pt, Au, Ag, etc.

Ore If one or more chemical elements occur in sufficient abundance that they may be mined for a profit, then the rock is termed an ORE.

Classification of Mineral Resources • Metallic Mineral Resources Abundant (Iron, Aluminum, Magnesium, Manganese, Titanium) Scarce (Copper, Lead, Zinc, Chromium, Nickel, Gold, Silver) • Non-Metallic Mineral Resources Construction (Sand, Gravel, Clay, Limestone, Gypsum) Agriculture/Industry (Phosphates, Nitrates, Sodium Chloride, Sulfur) Ceramics/Abrasives (Feldspar, Clay, Quartz, Diamond, Pumice, Garnet, Corundum) Building Materials: what did students do with their 9000 pounds of sand and gravel last year? That’s the per capita annual production in the US. Many cities are facing shortages of building materials, not because the materials are rare, but because residents object to having quarries and gravel pits nearby. The building stone industry in the US was almost extinct. Then stone became fashionable and within a few years in the 1980’s production of granite and marble increased tenfold. Ferrous Metals: recycled iron and steel now amounts to more dollar amount than mined iron. Gold and Silver: in 1965, the value of silver for photography climbed to the point where there was more than 25 cents worth of silver in a quarter. Even the Federal Government is smart enough to figure out that was a losing proposition, and stopped minting silver coins in 1965. During World War II, copper was in such demand for artillery shell casings that we minted steel pennies in 1943. To save on copper, wires at the Oak Ridge atomic facility were made of silver from the Treasury – it worked because the facility was under such tight security. By 1944 the copper shortage had eased and recycled shell casings were used to mint pennies. Collectors call 1944 and 1945 pennies “shell case” cents. Platinum is worth as much as gold, but is in such demand as a catalyst and for chemical uses that its value fluctuates wildly, so it is not used in coins very much.

Processes of ore concentration are related to rock formation. Rocks are grouped into three major families, based upon their processes of formation. Igneous Rocks Sedimentary Rocks Metamorphic Rocks

Ore formation by igneous processes Crystal Settling Dense minerals crystallizing in magma, settle to the bottom of the magma chamber Ex. – Chromium, Platinum, Nickel, Copper, Lead

Ore formation by igneous processes Hydrothermal enrichment water, superheated by magma, dissolves minerals and deposits them in “veins” Ex. – Copper, Gold, Silver

Ore Formation by Igneous Processes Lode – many thick mineral veins in a small region Ex. – The “Mother Lode” during the California gold rush

Hydrothermal Enrichment Pegmatites – “veins” in rocks Common form of gold enrichment Exhalites – Submarine vents of hot, mineral-rich water “Black Smoker Chimneys” – hydrothermal vents Associated with mid-ocean ridges

“Black Smokers”

Sulfide Mine in an Exhalite Deposit

Ore Formation by Sedimentary Processes Placer deposits Moving water erodes rocks releasing heavy minerals which settle on the bottom of stream beds (ex. – gold) Ex. - gold

Ore Formation by Sedimentary Processes Evaporite deposits Precipitation of salt in shallow marine basins or saline lakes (in arid climates) Ex. – halite, gypsum, borax

Ore Formation by Metamorphic Processes During contact metamorphism, pre-existing rock is altered forming ores Ex. – Lead, Copper, Zinc

Prospecting and Exploration Methods of Discovery: Satellite and Aerial Photography Remote Sensing Geological Mapping Magnetic Mapping Gravity Mapping Radioactivity Mapping Geochemical Sampling Electrical Sounding Ground-Penetrating Radar Seismic Methods Reflection - Detailed but Expensive Refraction - Cheap but Not Detailed Core Sampling and Well Logging

Economic Factors in Mining Richness of Ore Quantity of Ore Cost of Initial Development Equipment, Excavation, Purchase of Rights Operating Costs: Wages, Taxes, Maintenance, Utilities, Regulation Price of the Product Will Price Go up or down?

Issues in Mineral Exploitation Who Owns (Or Should Own) Minerals? Landowner Discoverer Government Unclaimed Areas: Sea Floor Antarctica Who Controls Access for Exploration? Remote Sensing vs. Privacy

Types of Mines Surface Subsurface (underground) Placer – dredging (Au) Open pit (Au, Cu) Quarries (stone, gravel, sand) Strip mines (coal) Subsurface (underground) Placer – dredging (Au) Seafloor– nodules (Mn, Ni, Fe)

Problems with Mining Safety Economic Impact Environmental Problems Mine Wastes/Pollution Hazardous working conditions Noise Economic Impact "Boom and Bust" Cycles Environmental Problems Exploration Construction & Operation Waste Disposal

Reclamation Returning the land to a more natural state after mining operations have ended Mine Albert, Quebec, before and after reclamation. Government of Quebec

Economic Implications Ores are not found everywhere Some ores are richer than others Ore distribution is a function of geology Ore distribution is not equal across the world Some nations are rich in mineral resources Other nations have few mineral resources No nation is self sufficient in mineral resources

Environmental Considerations Mining leaves holes in the ground Mining adds unusual quantities of sediment to rivers and streams Mining exposes minerals to interaction with surface and groundwater, which may contaminate them Mine waste may be unstable - landslides Smelting may pollute air and water

Why do we need mines?

We all make choices. Industrialized societies depend on mineral resources Environmental problems must be considered in extracting wealth from the Earth Its not Good (environment) vs. Evil (industry) It’s a compromise, of which, we must make the best!