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Chapter 12 -- Texas Natural Resources

Chapter 12 -- Texas Natural Resources - THE THIRD PLANET E...

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THE THIRD PLANET E. R. SWANSON – spring 2009 Texas Natural Resources Texas Metals Smelters and refineries in Dallas, El Paso (now closed), Laredo and along the Texas Gulf Coast result in a fairly impressive official list of metals produced in Texas. The truth is, however, that metal mining in Texas has not amounted to much. Only iron, magnesium, and uranium have been produced recently in Texas, and all of these metals have come from the Texas Gulf Coastal Plain or the immediate vicinity. Copper, gold, lead, silver and zinc have had very modest historic production, but only mercury mines of Trans-Pecos Texas have formed, in their day, a world class mining district. This text will cover the three most recently produced metals and three others of significant historic interest. Magnesium Magnesium is the third most abundant element dissolved in sea water, but it is well behind sodium and chlorine, the constituents in salt. Still, magnesium is useful in strengthening steel, as an alloy with aluminum and it also has some electrical uses. Dow Chemical extracts hydrous magnesium chloride from seawater at Freeport, Texas (Fig. 1), and then produces magnesium metal by electrolysis. Figure 1 – Metal Mining Regions of Texas 1
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THE THIRD PLANET E. R. SWANSON – spring 2009 Iron Iron has been mined in Texas since 1855 from very low-grade iron ores located in early Cenozoic sedimentary rocks near Rusk in East Texas (Fig. 1). The iron ore was originally processed into steel by convicts from the local state penitentiary. In more recent times, it has been mined and processed by the Lone Star Steel Company. The original source of the iron is an iron-bearing mineral called glauconite. Glauconite is a mineral formed by the chemical reaction between sea water and the fecal material from marine organisms, and glauconite formed from these fossil fecal pellets is abundant in some East Texas sandstone. Glauconite is mined as a product called greensand and is used directly as a soil additive, but it is hardly iron ore. Over millions of years, however, water percolating through the sandstone has dissolved iron from the glauconite and precipitated it as iron oxides, hydroxides and carbonates. From humble fecal beginnings, the material has ultimately formed what are appropriately called the brown iron ores of Texas. Uranium Uranium was discovered in Karnes County (Fig. 1) during the uranium boom of the 1950s, following the development of peaceful and some not so peaceful uses for atomic fission. Open pit mining was begun in 1961, and underground leach-mining was added in 1975. Gulf Coastal Plain uranium started its “life” locked in Cenozoic Trans-Pecos volcanic ash and volcanic rock fragments. Volcanic fragments were eroded, transported and deposited along with other Gulf Coastal Plain sediments. Because uranium is readily leached from volcanic material by passing, oxygen-rich ground water, it migrated from the source sedimentary rock fragments to where it encountered a reducing environment and was precipitated to fill any available rock opening. Such reducing environments may be
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Chapter 12 -- Texas Natural Resources - THE THIRD PLANET E...

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