<text><span class="style10">ining, Minerals and Metals (4 of 4)</span><span class="style7"></span><span class="style10">GEMS</span><span class="style7">Hundreds of stones are mined as gems. The most important is diamond (a form of carbon) because its great hardness makes it important for tools in industry. The major source of diamonds is South Africa, where they are recovered from rock by deep mining. Where gemstones have been eroded from rocks by water, they may be found in gravel deposits. Sapphires and rubies, for instance, occur in such deposits in Sri Lanka.</span><span class="style10"> METALS Element Abundance Major uses</span><span class="style7"> (mineral) </span><span class="style10">in crust</span><span class="style7"> (parts per million) Aluminum 81 000 Conductors, aircraft, (bauxite) ships, cars, foil Chromium under Chromium-plating, (chromite) 700 stainless steel Copper 100 Conductors, (many) alloys (brass, bronze), coinage, plumbing Gold under Source of value, (naturally 0.005 jewelry, some occurring) electronic uses Iron 50 000 Structures, machines Lead 20 Batteries, roofing, (galena) radiological protection Magnesium 25 000 Low-density alloys (magnesite, for aircraft, etc.) machinery, etc. Mercury under Explosives, scientific (cinnabar) 1 instruments, dentistry Nickel under Nickel-plating, steel (garnierite, 80 alloys, gas-turbine pentlandite) engines, coinage Platinum under Catalyst in chemical (naturally 0.005 processes and in car occurring, exhausts sperrylite) Silver under Jewelry, silverware, (many) 1 photographic emulsions Tin 1.5 Tin-plating, alloys (cassiterite) (bronze and pewter) Tungsten 1.5 Lamp filaments, (wolframite, electronics, steel scheelite) alloys, cutting tools Uranium under Nuclear power (pitchblende) 7 stations Zinc under Alloys (brass), (sphalerite) 80 galvanizing steel</span><span class="style10">COAL</span><span class="style7">Coal is a carbon-based mineral that formed over many millions of years as a result of the gradual compacting of partially decomposed plant matter. Three basic types of coal are found: lignite, bituminous coal and anthracite. Lignite (brown coal) has the lowest heat value, since it was formed more recently and contains less carbon and more water than the other varieties. About half the coal mined is used for generating electricity, with another quarter going to the steel industry as coking coal. The remainder is used in other industries or for home heating. In the past, coal was the chief raw material for the plastics industry, but in this function it has been largely superseded by crude oil.</span></text>
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<layer>background</layer>
<id>23</id>
<text>ΓÇó ELEMENTSΓÇó THE EARTH'S STRUCTUREΓÇó THE FORMATION OF ROCKSΓÇó ENERGY 1ΓÇó OIL AND GASΓÇó THE INDUSTRIAL REVOLUTION</text>
