Download Getting to Know: Minerals

Getting to Know: Minerals
Consider the following two common activities:
sprinkling a bit of salt on your food and flipping
on the lights. Do you think these activities share
anything in common? You might think these two
activities are completely unrelated, but they do
share something. Both activities involve minerals.
Salt is a mineral that we add to food. Electrical
wires are often made of copper, another mineral.
In fact, minerals are all around us. They’re very
important to our lives. Many common activities
and everyday products rely on minerals. We have
developed ways to mine them from the Earth and
refine them for our use. As you explore the ideas
in this concept, you’ll learn much more about
minerals.
We use minerals for many everyday
activities. Minerals are even in the food
we eat.
What are minerals and what are some of their common characteristics?
There are many different kinds of minerals with many different uses. All minerals share some common characteristics. Minerals are solid substances that occur naturally and are made of inorganic crystals. The term inorganic means nonliving. Minerals are considered a nonrenewable resource because they are often very slow to form. However, some minerals, like salt, form much more quickly.
Minerals and rocks sound like the same thing. Is there a difference
between minerals and rocks?
There is a difference between minerals and rocks. To understand how the two differ, we
have to look at their composition. Minerals are formed of molecules that bond in geometric
patterns. As a mineral crystal grows, these patterns are repeated. This repeating structure
produces forms that we recognize as crystals. Rocks, on the other hand, are made from one or
more minerals. There are hundreds of different kinds of minerals.
Misconception 1: I heard that minerals can easily be identified by their color.
Is this correct?
Scientists do consider the color of a mineral when they are classifying it. However, they
can’t rely on color alone. That’s because the color of a mineral is actually one of the least
reliable characteristics of a mineral. Some minerals can appear in a wide range of colors
because of factors like natural weathering of the mineral or impurities that might be
present in the mineral.
Concept: Minerals
Getting to Know
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Because there are so many different
minerals, have scientists developed
ways to classify them?
Minerals can be classified by their color
and shape, among other things.
Scientists have developed many criteria to help
classify minerals. They look at several different
characteristics of minerals to help identify them.
These characteristics include the shape of the
crystal, cleavage, fracture, hardness, and specific
gravity. Scientists also look at the mineral’s ability
to transmit light, and its color, luster, and streak. In
addition, scientists classify minerals based on the
elements they are made from and by the way the
atoms are arranged.
Let’s look at a few of those characteristics in greater detail. Streak is the color of a mineral
when it is finely ground into a powder. Sometimes a mineral’s streak is the same as its color,
but the streak can also be different than the color of the solid mineral. A tool called a streak
plate is used to help determine the streak of a mineral. A streak plate is white porcelain that’s
just rough enough for a mineral to leave a fine powder residue when it is scraped across the
plate. A mineral’s cleavage is how it breaks. Some minerals break along clearly defined lines,
where atomic bonds in the mineral are weaker. Not all minerals show clearly defined cleavage.
Imagine you come across a mineral and you want to identify it. By studying all of the
characteristics mentioned, you can narrow down the mineral until you can identify it.
Sometimes, even when scientists examine a mineral, it can be difficult to identify. This is
because some minerals have variations in them. Other minerals can have impurities. However,
the characteristics mentioned do help scientists make informed identifications.
You’ll learn about the other characteristics of minerals as you explore this concept in greater
depth.
Misconception 2: I think I understand a lot more about minerals now. Does the
property of hardness refer to how easily a mineral breaks?
A mineral’s hardness isn’t determined by how easily a mineral breaks. Rather, hardness of
a mineral is actually a measure of its resistance to being scratched. The more resistant a
mineral is to scratching, the greater its hardness.
Concept: Minerals
Getting to Know
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© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.