Chapter 3: Patterns in Nature: Minerals
Study Plan
Crystals formed by precipitation from a solution may grow inward from the walls of a container. Geodes are a spectacular example of this phenomenon.
Credit: Stephen Marshak
Guide to Reading
Although there are about 4,000 recognized minerals, only a few dozen are common on Earth. (See Table 3.1 [link]) If you're fortunate enough to be taking this as a lab class or if you have access to a mineral collection, you'll probably find samples of the common minerals in your collection. Do look at them as you read along. Nothing beats hands-on for mineral identification and appreciation.
Most of Chapter 3 is devoted to the scientific approach to mineral study, but woven throughout the chapter are consumer-type topics:
- advances in mineralogy made possible by use of optical and electron microscopes and X-ray diffraction equipment
- the questionable magical powers of crystals
- the beauty and legends of gemstones (diamonds and more)
The author begins with a very detailed definition of minerals. This leads quite naturally into a discussion of crystal formation and crystals' unique internal structures, which determine their external shapes and symmetry.
Mineral identification is the next topic. How do you tell one kind from another when there are so many? Fortunately there are few enough common ones that examination of a few physical properties generally allows identification of specimens in either the field or the lab.
Keeping things organized is a challenge when dealing with large numbers of anything. Since minerals are simply chemical elements or compounds formed naturally on Earth, it's logical and useful to study them as chemical groups. Minerals that are single elements are part of the group native metals. Most minerals that are compounds fit into one of the following chemical groups:
- silicates
- oxides
- sulfides
- sulfates
- halides
- carbonates
The chapter leaves many practical questions unanswered, including questions dealing with mankind's use of minerals as resources for manufacturing products and producing energy. These issues are dealt with later in the book, in Chapter 12. For now the author pursues the fact that minerals are the building blocks of rocks, and the next three chapters deal with the very geologic topics of igneous, sedimentary, and metamorphic rocks.
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