Overview
Minerals make up rocks. They are natural rather than synthetic, inorganic, and solid. Minerals have a distinct crystalline structure and chemical composition.
Types of Elements
The most common elements that are naturally found in the earth’s crust are oxygen, silicon, aluminum, iron, calcium, magnesium, potassium, and sodium. Other elements are much less common. Although there are more than 100 elements in the periodic table, not all of them are found naturally in any quantity, and some of the radioactive elements have already decayed into others.
Minerals are Inorganic
Organic substances, such as coal and oil, were once part of living organisms. Coal is a rock, but not a mineral. It is naturally occurring, is distinct chemically, and is solid. Oil is also naturally occurring, but it is not solid, and it doesn’t have a crystalline structure. However, one of the most common rocks, granite, is made up of distinct minerals. They are shown as differently-colored flecks of pink feldspar, white quartz, and black amphibole.
Crystalline Structure
Another characteristic of minerals is that they have a distinct crystalline structure. Within any crystal, atoms of different elements are arranged in fixed symmetry. For example, salt (NaCl) is found in cubic crystals, with sodium ions alternating with chlorine ions. Other minerals form other types of solid crystals, such as octahedrons or dodecahedrons. Quartz is a common mineral that forms elongated crystals in the shape of prisms.
Chemical Composition
Minerals are composed of chemicals that are always combined with particular bonds; and elements that form those chemicals are in specific ratios. Any mineral can be described by a chemical formula. Although precious metals such as gold (Au) and silver (Ag) are usually in crystals of single elements, most minerals are composed of more than one element. For example, the formula for quartz (SiO2) means that each molecule of quartz contains one atom of silicon bonded with two atoms of oxygen. If the mineral had another chemical composition, it would be some other substance. Also, the chemical composition of a mineral often determines its properties and how often it occurs. Quartz is a common mineral because both silicon and oxygen are the most common elements in the earth’s crust.
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