Earth Science for Kids
What is a mineral?
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.
What is the difference between a mineral and a rock?
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.
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.
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 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 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.
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.
Interesting Facts about Minerals
- 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 mineral 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.
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