Environmental Problems, Their Causes, and Sustainability 1

What Are Nonrenewable MineralResources? Useful Rock ResourcesMineral resources are nonrenewable materialsthat we can extract from the earth’scrust.A nonrenewable mineral resource is a concentrationof naturally occurring material in or on the earth’scrust that can be extracted and processed into usefulmaterials at an affordable cost. Over millions to billionsof years the earth’s internal and external geologicprocesses have produced numerous nonfuel mineralresources and fossil fuel energy resources. Becausethey take so long to produce, they are classified as nonrenewableresources.We know how to find and extract more than 100nonrenewable minerals from the earth’s crust. Theyinclude metallic mineral resources (iron, copper, aluminum),nonmetallic mineral resources (salt, clay, sand,phosphates, and soil), and energy resources (coal, oil,natural gas, and uranium).Ore is rock containing enough of one or moremetallic minerals to be mined profitably. We convertabout 40 metals extracted from ores into many everydayitems that we either use and discard (Figure 3-18,p. 53) or learn to reuse, recycle, or use less wastefully(Figure 3-19, p. 53).The U.S. Geological Survey divides nonrenewablemineral resources into four major categories (Figure16-10):■ Identified resources: deposits of a nonrenewablemineral resource with a known location, quantity, andDecreasing cost of extractionUndiscoveredOtherresourcesDecreasing certaintyExistenceIdentifiedReservesKnownFigure 16-10 Natural capital: general classification of mineralresources. (The area shown for each class does not representits relative abundance.) In theory, all mineral resources classifiedas other resources could become reserves because of risingmineral prices or improved mineral location and extractiontechnology. In practice, geologists expect only a fraction ofother resources to become reserves.Not economical Economicalquality, or whose existence is based on direct geologicevidence and measurements■ Reserves: identified resources from which a usablenonrenewable mineral can be extracted profitably atcurrent prices■ Undiscovered resources: potential supplies of anonrenewable mineral resource assumed to existon the basis of geologic knowledge and theory butwith unknown specific locations, quality, andamounts■ Other resources: undiscovered resources and identifiedresources not classified as reservesMost published estimates of the supply of a givennonrenewable resource refer to reserves. Reserves canincrease when new deposits are found or when higherprices or improved mining technology make it profitableto extract deposits that previously were too expensiveto extract. Theoretically, all other resourcescould eventually be converted to reserves, but this ishighly unlikely.16-5 FINDING, REMOVING, ANDPROCESSING NONRENEWABLEMINERAL RESOURCESHow Are Buried Mineral Deposits Found?Underground Detective WorkPromising underground deposits of minerals arelocated by a variety of physical and chemicalmethods.Mining companies use several methods to find promisingmineral deposits. One is using aerial photosand satellite images to reveal protruding rock formations(outcrops) associated with certain minerals.Also, planes can be equipped with radiation-measuringequipment to detect deposits of radioactive mineralssuch as uranium ore, and a magnetometer to measurechanges in the earth’s magnetic field caused by magneticminerals such as iron ore. Another method uses agravimeter to measure differences in gravity caused bydifferences in density between an ore deposit and thesurrounding rock.Underground methods include drilling a deepwell and extracting core samples. Scientists can alsoput sensors in existing wells to detect electrical resistanceor radioactivity to pinpoint the location of oiland natural gas. Scientists also make seismic surveys onland and at sea by detonating explosive charges andanalyzing the resulting shock waves to get informationabout the makeup of buried rock layers. Yet anothermethod is to perform chemical analysis of waterand plants to detect deposits of underground mineralsthat have leached into nearby bodies of water or havebeen absorbed by plant tissues.340 CHAPTER 16 Geology and Nonrenewable Mineral Resources