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Guide to Reading
This chapter deals with many of the geologic resources that give us the raw materials for our very comfortable lifestyles in our industrial society. It discusses the geologic reasons for their existence, methods of extracting them from the Earth, products made from them, concerns about future supplies, and the environmental impact caused by their extraction.
The raw materials are both metallic and nonmetallic mineral resources. The metals are generally less abundant and more expensive than the nonmetals. Some are not only useful to humankind but are highly prized by society. The native metal, gold, influenced the course of history in our own West and in other places worldwide. The author discusses gold and many more mundane metals (including copper, tin, iron, aluminum, lead, zinc, and manganese). Topics of discussion are:
- What are metallic characteristics and how do you work with metals? You read about metallic bonds, metallurgy, malleability, tempering, cold working, native metals smelting, slag, alloys like bronze and steel, precious metals, and base metals.
- How do you extract metals from the Earth? You read about underground mining, open pit mines, ores, ore minerals, grade of an ore, shows, assays, adits, and rock bursts.
- How can you classify ore deposits? On the basis of their origins: magmatic (including massive-sulfide deposits), hydrothermal (including disseminated, vein, and porphyry deposits, and black smokers), secondary-enrichment deposits (including copper carbonates like azurite and malachite, and MVT ores of lead and zinc), sedimentary deposits (including banded-iron formations and manganese nodules), residual mineral deposits (like bauxite, that are left after leaching by groundwater), and placer deposits (of dense materials).
- Where do you look for ore deposits? Metallic minerals aren’t evenly distributed worldwide. Why are deposits found in some places and not in others? Plate tectonics, of course! You get details of ores in the Andes of Peru and in the western United States. You’ve gotten so used to plate tectonics’ being the reason for everything, you may be surprised to learn plate tectonics had no direct bearing on the formation of banded-iron formations (BIFs) or on residual ore deposits like bauxite.
In all those discussion of metals, and throughout the rest of the chapter, the author has had to make choices of what examples he’ll use. While it’s never a bad idea to learn as much detail as is reasonable, it’s most important you understand the concepts being explained by use of the examples. Your teacher may use local examples of minerals to illustrate concepts.
Nonmetallic mineral resources don’t have the glamour of gold, but they’ve been equally useful to humankind. Centuries ago people began to quarry stone to construct impressive and enduring buildings, and as time has passed, society has continued to use building stone and numerous other nonmetallic resources. The chapter mentions many of these resources and products made from them, including cement, concrete, gravestones, flagstones, bricks, crushed rock, window glass, asbestos, landscaping rock, salt, and gypsum.
As Chapter 14 pointed out, society has become very concerned about the diminishing amounts of energy reserves; it is also starting to be concerned about diminishing amounts of mineral reserves. As with energy resources, mineral resources are nonrenewable and unevenly distributed around the world. This causes economics and politics to play important roles in any scenario that concerns mineral reserves. How long a resource lasts depends in part on how badly people want it and what they’re willing to pay for it. Many of these materials have been fought over in the past; the United States stockpiles some of its strategic metals to hopefully avoid some battles in the future.
The chapter ends with the sensitive topic, mining and the environment. Even if things run smoothly in the political sense, extracting minerals on a large scale can be costly to the environmental quality on Earth. We want all the good things of life Earth can supply. Balancing our material desires with minimal environmental impact is becoming a growing challenge. |
