Chapter 10 -- Industrial Materials

Chapter 10 -- Industrial Materials - THE THIRD PLANET E. R....

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THE THIRD PLANET E. R. SWANSON – spring 2009 INDUSTRIAL MINERALS Introduction While anthropologist go to great length and archeologist go to great depths to study Stone Age people, in many ways modern humans have never left the Stone Age. The fact is that people today use far more stones than did our ancient ancestors; we just use the more modern sounding term of industrial minerals. Industrial minerals are nonmetallic rocks and minerals, typically consisting of low-value materials used in large amounts, mostly by industry (hence the name). Industrial minerals have essentially very little value. Their price mostly reflects the cost of mining, processing and transportation. Industrial minerals are usually abundant and widespread and typically mined to satisfy a local demand. A few examples include: crushed rock, building stone, sand and gravel, cement, asbestos, salt and the minerals constituents of fertilizer. Sand and Gravel Sand and gravel are essential construction materials. Sand and gravel are typical extracted from stream beds where nature has already done most of the work by breaking up the material and sorting according to size. Sand and gravel may be combined with cement to make concrete, a commodity with a more interesting history. Cement Ancient Greek buildings were constructed with blocks piled on top of other blocks. Cement was a later Roman invention. You can see how the Romans used cement in the mortar holding bricks together in the Coliseum at Rome. But whoever was put in charge of writing down all the knowledge as Rome fell and European intellectual lights went out during the Dark Ages, must have forgotten to include the formula for making cement. The recipe was rediscovered centuries later, in 1824, by Englishman, Joseph Aspidin, who patented the formula for what is called Portland cement. Apparently, the artificial rock that Aspidin made just happened to look a great deal like Portland Stone, a rock quarried and used in the day, and the name Portland stuck to the cement. The recipe for Portland cement starts with limestone (CaC0 3 ), a good source for the lime (Ca0) that cement needs and cement’s major ingredient by a factor of ten. It should be no surprise, then, that cement plants are located next to limestone exposures near big cites. San Antonio has had its share of limestone quarries over the years. As you drive away from the city you pass abandoned limestone quarries that have been left behind for the bears at the City Zoo, for students at Trinity University, shoppers at The Quarry and La Cantera (Cantera means quarry) and thrill seekers at Fiesta Texas. Cement also needs a source of alumina (Al 2 O 3 ) and silica (SiO 2 ), and the sedimentary materials typically used for this purpose are shale or clay . It would be beneficial for cement economics if the cement plant was located next to limestone interlayered with shale at about a ratio of 1 part shale to 9 parts limestone. Although other ingredients 1
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This note was uploaded on 09/09/2009 for the course GEO 301 taught by Professor Long during the Spring '07 term at University of Texas at Austin.

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Chapter 10 -- Industrial Materials - THE THIRD PLANET E. R....

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