Guide
to Reading 
Although there are over 3,000 recognized minerals,
only a few dozen are common on Earth. 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 all of these 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 such as the questionable magical powers of crystals and 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
- Sulfates
- Oxides
- Halides
- Sulfides
- 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 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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