Minerals are solid substances that occur naturally. They can be made from a single element (like gold or copper) or from a combination of elements. The Earth is made up of thousands of different minerals. Minerals have a specific chemical structure which is the same throughout the entire mineral. Rocks, on the other hand, are composed of a variety of different minerals and are not consistent throughout their structure.
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Characteristics of Minerals
Some common characteristics of minerals include:
- Solid – All minerals will be solids at normal temperatures on Earth.
- Naturally occurring – Minerals occur in nature. Solids that are made in a chemistry lab don’t count as minerals.
- Inorganic – Minerals don’t come from plants, animals, or other living organisms.
- Fixed chemical structure – Specific minerals will always have the same chemical formula. They will have the same combination of elements. Minerals also generally are formed with a crystal structure.
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Properties of Minerals
Different minerals are often defined by the set of properties described below:
- Luster – Luster describes how well a mineral reflects light. Examples of luster include glassy, metallic, brilliant, and dull.
- Hardness – The hardness describes how easy it is to scratch the surface of a mineral. Scientists often use the Moh’s scale to describe hardness. Using the Moh’s scale, a “1” is the softest mineral and a “10” is the hardest. One example of hardness is the diamond. Diamond has a hardness of 10 because it is the hardest of all the minerals.
- Streak – Streak is the color of the mineral in powdered form. One way to determine the streak is to rub the mineral across a rough hard surface like a tile.
- Cleavage – Cleavage describes how a mineral breaks up into pieces. Some minerals break up into small cubes while others may break up into thin sheets.
- Specific Gravity (SG) – The specific gravity measures the density of the mineral. It is measured in comparison to water where water has a specific gravity of 1. For example, pyrite has a specific gravity of 5 and quartz has a specific gravity of 2.7.
- Color – Although the color is often used to describe a mineral, it sometimes isn’t the best way to tell one mineral from another as one type of mineral can come in several different colors.
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Types of Minerals
There are many different types of minerals, but they are often divided into two groups: silicates and non-silicates. Silicates are minerals that contain silicon and oxygen. Over 90% of the Earth’s crust is made up of silicates. The rest of the minerals are lumped into a group called non-silicates.
Some important non-silicate minerals include:
- Carbonates – Carbonates contain carbonate (CO3) combined with some other element. Calcite is a mineral made from carbonate and calcium.
- Halides – Halides contain a halogen element as the main element. Table salt (NaCl) is a halide mineral made from the halogen chlorine (Cl) and sodium (Na).
- Oxides – Oxides are minerals where the main element is oxygen. Chromite is an oxide mineral made from iron, chromium, and oxygen.
- Sulfides – Sulfides contain sulfur and one or more metals or semimetals. Pyrite is a sulfide made from iron and sulfur.
Native elements such as copper, gold, diamond, graphite, and sulfur can be thought of as a third group of minerals.
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Facts about Mineral
- Scientists who study minerals are called mineralogists.
- Around 99% of the minerals in the Earth’s crust are made up of eight elements including oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium.
- Common minerals include quartz, feldspar, bauxite, cobalt, talc, and pyrite.
- Some minerals have a different colored streak than the color of their body.
- A gem is a piece of rare minerals such as diamond, emerald, or sapphire that is cut and polished to shine.
- Certain minerals are needed by our bodies so we can grow healthy and strong.