Mineral
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Minerals are substances that are formed naturally in the Earth. Minerals must be solid, inorganic, have a crystal structure, and be naturally happening. The study of minerals is called mineralogy.
A mineral is a solid and has a crystal structure. It also has a placed as chemical composition.
A mineral can be a hard object chemical element or in most cases a solid compound. Two common minerals are quartz and feldspar.
There are over 4,000 known minerals.
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[change] Minerals have four types
People use minerals all the time. Every time people turn on a microwave oven or a TV people need minerals. The copper in the wires that carry electricity to the object is a mineral. Table salt or halite, is another mineral that people use in their everyday life. Minerals have four types. A mineral is a substance that
- forms in wildlife
- is a solid
- has a definite chemical makeup
- has a crystal structure
People might think that minerals and rocks are the same things. But a mineral must have the four types. A rock has only two of these characteristics—it is a solid and it forms naturally. A rock usually contains two or more rypes of minerals. Two samples of the same type of rock may vary greatly in the amounts of different minerals they contain. Minerals, however, are always made up of the same materials in the same proportions. A ruby is a mineral. Therefore, a ruby found in India has the same makeup as a ruby found in Australia. Indeed rocks are not the same as minerals.
[change] Formed in Nature
Minerals are formed by natural processes. Every type of mineral can form in nature by processes that do not involve living things. As people will read, a few minerals can also be produced by things as part of their shells or bones.
Minerals form in many ways. The mineral halite, which is used as table salt, forms when water evaporates in a hot, shallow part of the ocean, leaving behind the salt it contained. Many types of minerals, including the ones in granite makes when molten rock cools. Talc, a mineral that can be used to make baby powder, forms deep in Earth as high pressure and temperature causes changes in solid rock.
[change] Solid
A mineral is a solid—that is, it has a definite volume and a rough shape. Volume refers to the amount of space an object takes up. For example a golf ball has a smaller volume than a baseball, and a baseball has a smaller volume than a basketball.
A substance that is a liquid or a gas is not a mineral. However, in some cases its solid form is a mineral. For instance, liquid water is not a mineral, but ice is.
[change] Definite chemical Makeup
Each mineral has a definite chemical makeup: it consists of a specific combination of atoms of certain elements, which makes some of them smell. An element is a substance that contains only one type of atom. In turn, an atom is the smallest particle an element can be divided into. Everything people can see or touch is made up of atoms. Some substances, including the minerals gold and copper, consist of just one element. All the atoms in gold or copper are of the same type. However, most items contain atoms of more than one element. Most minerals are compounds, substances consisting or several elements in specific proportions. Halite, for example, has one atom of sodiun for every atom of chlorine. The types of atoms that make up a mineral are part of what makes the mineral unique. The way the atoms are bonded, or joined together, is also important. Many properties of minerals are related to how strong or weak the bonds are.
[change] Crystal Structure
If people look closely at the particles of ice that make up frost, people will notice that they have smooth, flat surfaces. These flat surfaces form because of the arrangement of atoms in the ice, which is a mineral. Such an internal arrangement is a characteristic of minerals. It is the structure of a crystal, a solid in which the atoms are arranged in an orderly, repeating three-dimensional pattern. Each mineral has its own type of crystal structure. In some cases, two minerals have the same chemical composition but different crystal structures. For example, both diamond and graphite consist of just one element—carbon. But the arrangements of the carbon atoms in these two minerals are not the same, so they have different crystal structures and very different properties. Diamonds are extremely hard and have a brilliant sparkle. Graphite is soft, gray, and dull. In nature, a perfect crystal is rare. One can grow only when a mineral is free to form in an open space—a condition that rarely exists within Earth's crust. The photographs on page 47 show examples of nearly perfect crystals. The amount of space available for growth intluences the shape and size of crystals. Most crystals have imperfect shapes because their growth was limited by other crystals forming next to them.
[change] Minerals are grouped according to composition
Scientists classify minerals into groups on the basis of their chemical makeups. The most common group is the silicates. All the minerals in this group contain oxygen and silicon—the two most common elements in Earth's crust—ioined together. Though there are thousands of different minerals, only about 30 are common in Earth's crust. These 30 minerals make up most rocks in the crust. For that reason, they are called rock-forming minerals. Silicates, which make up about 90 percent or the rocks in Earth’s crust, are the most common rock-forming minerals. Quartz, feldspar, and mica are common silicates. The second most common group of rock-forming minerals is the carbonates. All the minerals in this group contain carbon and oxygen joined together. Calcite, which is common in seashells, is a carbonate mineral. There are many other mineral groups. All are important, even though their minerals may not be as common as rock-forming minerals. For instance, the mineral group known as oxides contains the minerals from which most metals, such as tin and copper, are refrned. An oxide consists of an element, usually a metal, joined to oxygen. This group includes hematite, a source of iron.
[change] Some uses of minerals
[change] Minerals and rocks
Minerals are different from rocks. A mineral is a chemical compound with a given composition and a defined crystal structure. A rock is a mixture of one or several minerals, in varying proportions.
