Feedstocks from the Geosphere

The geosphere is a source of a large number of feedstocks that are taken from it in the form of minerals. These include all the metals that are refined from metal-bearing ores including sources of iron aluminum copper lead zinc and, as discussed in Chapter 9, Section 9.3, the rare earths that are very important in modem technology-based societies. Also taken from the geosphere are fuels including fossil fuels such as coal and uranium used in nuclear reactors, which are discussed in Chapter 17. 

Underground mining has also caused numerous problans. Surface subsidence can be a problem with many relatively shallow underground mines. Aquifers have been disturbed and contaminated by improperly designed and operated underground mines. Water contamination can come from several sources. In the case of metal mines, water may become polluted with metals such as lead, copper, and zinc. A substantial water pollution problem has resulted from the exposure of iron pyrite, FeS2, to air. As discussed in some detail in Chapter 3, Section 3.5.1 microbial and chemical action produces sulfuric acid and soluble iron from this mineral, causing substantial water pollution problems. 

Desired minerals are always mixed with other rocks that must be separated. In many cases, particularly for more valuable metals, the mineral that is sought is less than 1% of the ore. This requires processing of the ore, a procedure called beneficiation, which produces relatively large amounts of finely divided by-product rock. For economic reasons, beneficiation is usually carried out at the mine site with the residues returned to the mine or left in piles at the site. As a result, water pollution problems may develop from the leaching of mine spoils. Some communities in the vicinity of lead mines have been contaminated by lead from mine residues, with particular concern over the health of exposed children. Spoils from iron mining in Minnesota have contaminated water with an asbestos-like mineral associated with the iron ore, requiring remedial action that has cost millions of dollars. Enormous piles of tar-contaminated sand are left over from the extraction by hot water of heavy crude oil from tar sands in the Canadian province of Alberta. 

---