Download The Basics of Minerals

The Basics of Minerals
Minerals, quite simply, are the building blocks for making rocks, and a rock is made up of one or more minerals. When you look at a
rock and see different colors, those colors are minerals that make up that specific rock. There are over 3,000 named minerals!
All rocks are made of natural nonliving solid substances called minerals. Minerals are formed from elements like oxygen, hydrogen,
and sodium. Elements are the simplest substance that can exist. Chemical elements, like oxygen, are arranged in a certain way or
pattern in a mineral. That arrangement is the mineral’s chemical composition. Every mineral has a different chemical composition. It
is like the mineral’s fingerprint. Minerals made of just one element are called native minerals. Some native minerals are made from
the elements gold, silver, copper, or mercury. Most minerals are combinations of two or more elements. These minerals are called
compounds. Salt is made from two chemical elements, sodium and chlorine. A specific mineral is always made up of the same
elements, no matter what kind of rock it forms. Some rocks, like limestone, are made of only one mineral. Other rocks have more
minerals. This is because heat or pressure forced many different minerals together to create the rock. Most rocks have between 2 and
10 minerals.
How Do Minerals Form?
Many rocks contain pockets of a single mineral. These pockets often form along with the rocks around them. Some minerals, such as
rubies, form as magma cools into igneous rock. Rubies are red stones used to make jewelry. The heat and pressure that form
metamorphic rocks can turn existing minerals into new minerals. Rocks known as jade form this way. Jade is often made into jewelry.
Other minerals form in hot springs, where hot water that is full of dissolved minerals flows to Earth’s surface from under ground. In
time, the water dries up, leaving minerals behind. Because minerals form all rocks, they are an important part of the rock cycle. This
cycle has been shaping Earth’s surface for millions of years.
Crystals and Chemistry
The atoms in a mineral are always arranged in a particular pattern. Atoms are able to arrange themselves in these various patterns
through a tiny electrical charge they give off. This charge causes some of the atoms to stick together. The atoms that stick together in a
mineral are called crystals. Geologists study the crystals’ patterns to figure out what kind of mineral they are looking at. Crystals come
in many different shapes. The mineral halite has crystals that are shaped like cubes. The mineral zircon has crystals that are shaped
like two pyramids that are stuck together. Crystals can also have smooth, flat sides, called faces. If you broke a mineral into tiny
pieces, every crystal inside each piece would have the same pattern.
Chemistry and crystal structure are two main ways in which minerals are classified, or grouped. A mineral’s chemistry means the mix
of different elements that make up that mineral. Its crystal structure is the way that the tiniest parts of each mineral, its atoms, are put
together. Two or more minerals can have the same crystal structure but be made up of different chemicals. Two or more minerals also
can have the same chemical makeup but have different crystal structures. These are called polymorphs. Crystal structure and
chemistry work together to decide a mineral’s properties.
Properties of Minerals
A mineral’s properties make it look and react differently from other minerals.
Properties can be used to identify, or name, minerals. Many minerals are known
for having a special color. Minerals also have luster, looking shiny or dull the
mineral looks. Minerals also can have a streak. This is the color that appears
when a mineral is rubbed against something. It is sometimes different from the
mineral’s color. Minerals can be classified in other ways, such as their specific
gravity, magnetism, how they break, or their hardness.
Color is a clue that geologists use to recognize minerals. Sulfur is a mineral that is always yellow. Other minerals, such as fluorite,
come in many colors. However, some minerals appear one color in daylight and glow a different color in ultraviolet light. This is
called fluorescence. Fluorite always glows blue in ultraviolet light. A mineral’s streak, or the color it leaves behind when rubbed
against a white tile, is another clue. Fluorite always leaves a white streak.
Geologists use the properties of minerals to figure out which minerals are which. One property they study is luster, or how minerals
shine. For example, the minerals topaz and emerald shine like glass, while graphite has a dull luster. Crystal habit, or the special shape
each mineral’s crystals take, is another clue geologists use to recognize minerals. Silver crystals are always in a cube shape.
Geologists also study a mineral’s cleavage, or how it breaks. The mineral muscovite splits in one direction into flat layers. Fluorite
splits into pieces shaped like diamonds. Quartz breaks into pieces with round edges.
Taste, Odor, and Magnetism
Taste and odor are also physical properties of minerals. You should never lick a mineral to see what it tastes like, though, because
some are poisonous. There are, however, minerals that are not poisonous and that have a strong taste. The most common of these
minerals is halite. The salt we use on our food is made from halite. Most minerals do not have a strong smell. That can change if the
mineral is heated or struck very hard. The mineral barite has no odor until it is heated. Then it smells like rotten eggs! There are a few
minerals that are magnetic. These minerals are very easy to identify. Magnetite got its name because it is magnetic. This mineral
draws other metals to it. These kinds of physical properties can provide some clues to a mineral’s identity.
Mohs’ Scale
Scientists would not be able to use hardness to identify a mineral if the Mohs’ scale did not exist. In 1822,
a scientist named Friedrich Mohs invented a scale that shows the hardness of different minerals by
scratching them. The Mohs’ scale lists how hard 10 common minerals are. The scale goes from 1 to 10.
The mineral that is listed as number 1 is the softest mineral. The mineral listed as number 10 is the
hardest. Talc is number 1 on the Mohs’ scale. It is so soft you can scratch it with your fingernail. Diamond
is number 10 on the Mohs’ scale. Only a diamond can scratch another diamond! The Mohs’ scale does not
list every mineral. Instead it lists 10 common minerals that have different levels of hardness. Using the
Mohs’ scale is a simple and useful way to get an idea of how hard a mineral is.
Diamonds are the world’s hardest minerals. These stones can scratch all other minerals, but no other
minerals can scratch diamonds. Because diamonds are so hard, bits of diamond are on the tips of dentists’
drills. Diamonds are often used to make jewelry. Many diamonds are cut at different angles to show a
rainbow of colors as light hits them. Billions of years ago, diamonds formed deep under ground under very high heat and pressure.
These stones are sometimes brought to Earth’s surface by volcanoes. Diamonds are so hard that even hot magma cannot melt them.
Oxides and Sulfides
Oxides and sulfides are two large groupings of minerals. They make up many of the compounds you see every day. Oxides are
compounds that have the element oxygen in them. They make compounds with many useful metals, such as iron, that are mined, or
dug from the ground. Sulfides are compounds that have the element sulphur in them. They also make compounds with metals and can
be mined. Pyrite is the name for iron sulfide. It is also known as fool’s gold because it looks a lot like gold.
Metals
Some minerals, like gold and platinum, are metals that occur naturally in Earth’s crust. Gold can be found in cracks in Earth’s crust.
These places are called veins. Veins of gold are often pushed to the surface because of pressure within Earth. Pure gold is almost
impossible to destroy but is soft enough to be shaped. Platinum, found in mines, is one of the heaviest substances on Earth. It is hard
and usually used to make jewelry. Sometimes metals combine to form compounds called alloys. Copper and zinc combine to form
brass. Tin and copper make the alloy bronze.
Some minerals are called precious metals. These are minerals that are made up of one metallic element. They are called precious
because they are uncommon and have a high value for many people. Because of their value, some precious metals, such as gold and
silver, have been used as money. Precious metals have a few properties in common. They do not often mix with other elements to
form compounds. Many have a shiny luster and need a lot of heat before they will melt.
Silicates
Silicates are the largest group of minerals. They are made of the elements silicon and oxygen, which then form compounds with other
elements. Aluminum, iron, and calcium are a few examples of common minerals that form silicate compounds. Because they are so
common, silicates make up at least a part of most of Earth’s rocks. That means that almost every rock you pick up likely has silicates
in it. Silicates can be found in quartz, as well as in many gemstones.
Carbonates and Sulfates
Carbonates and sulfates are mineral groupings that have some things in common. Carbonates are compounds that have the element
carbon in them. They most often form compounds with minerals such as calcium. Sulfates are another kind of compound that has the
element sulphur in it. They most often form compounds with the same kinds of elements with which carbonates form compounds.
Both carbonates and sulfates tend to form in places where salt water evaporates.
Halides
Halide minerals are often thought of as different kinds of salts. Halides are compounds that have the elements flourine, chlorine, or
iodine in them. The salt in your kitchen is a compound of the elements sodium and chlorine. As are the sulfates, halides often form
where salt water evaporates. You can see halides in places such as the Bonneville Salt Flats, in Utah.
The Importance of Minerals
Minerals are important in different ways. Without minerals we would not have salt to put on our food or graphite to put in our pencils.
Metals are used to build houses, cars, furniture, and many other things. Copper is one of the most useful metals because it is very good
at carrying electricity. Copper wires carry electricity through most homes. Iron, lead, aluminum, and other metals are used to make
machines and other tools. We mix minerals to make cement to holds together bricks in buildings. The mineral mica is found in most
rocks. It is used to make computers. Quartz is used to make glue, glass, and paint. Paint also often contains talc. Minerals make up all
the rocks on Earth. Without minerals there would be no rocks, and the rock cycle would not exist. Minerals are a very important part
of shaping and reshaping Earth’s surface.