Chapter Introduction

Lesson 1 What is a mineral?

Lesson 2 How are minerals identified?

Lesson 3 Sources and Uses of Minerals

Chapter Wrap-Up Mark Schneider/Getty Images

• A mineral is a naturally occurring, inorganic solid with a definite chemical composition and an orderly arrangement of atoms or ions.

• There are approximately 4,000 minerals on Earth, but only about 30 are common.

What is a mineral?

• Of the 30 common minerals, ten are rock-forming minerals, including quartz, feldspar, and olivine.

• These minerals occur naturally and are not made in a laboratory.

What is a mineral? (cont.)

• Minerals have a definite chemical composition.

• Some minerals, such as silver and sulfur, are composed of just one element. These are known as native elements.

• Other minerals are made up of a combination of several elements.

What is a mineral? (cont.)

• Minerals form predictable crystal patterns.

• The internal arrangement of atoms or ions determines the shape of a crystal.

What is a mineral? (cont.)

A crystal is a solid with a repeating arrangement of atoms or ions in 3 directions.

What is a mineral? (cont.)

• Minerals are solids, meaning they exhibit an orderly internal arrangement of atoms or ions.

• Minerals are inorganic, or not from biologic origins.

• Despite being inorganic, some minerals can form as a result of organic processes.

What is a mineral? (cont.)

• Minerals occur in many different shapes.

• When a crystal forms under the right conditions and has time to grow, it will develop a characteristic crystal shape.

• Most of the time, minerals grow in tiny clusters.

The Structure of Minerals

• The common rock-forming minerals are composed of combinations of elements that are abundant in Earth’s crust.

• Oxygen and silicon are the two most abundant elements in the crust.

The Structure of Minerals (cont.)

• The two main families of rock-forming minerals are the silicates and the nonsilicates.

• A silicate is a member of the mineral group that has silicon and oxygen in its crystal structure.

• Nonsilicate minerals do not contain silicon.

The Structure of Minerals (cont.)

• All minerals form through crystallization.

• The process of crystallization occurs when particles dissolved in a liquid or a melt solidify and form crystals.

• The chemical and physical properties of minerals can help geologists infer the type of environment where these minerals formed.

How do minerals form?

• Minerals can crystallize from either hot or cool solutions.

• As water evaporates from a cool solution in a dry environment, solids crystallize out of the water and form minerals.

• Sometimes minerals can crystallize from water in environments that aren’t dry.

How do minerals form? (cont.)

• Hot solutions are made when water flows through cracks in the crust into deep and hot environments.

• Sometimes hot solutions carry large concentrations of dissolved solids that eventually become valuable mineral deposits.

How do minerals form? (cont.)

• Minerals can also form from magma. Magma is molten material stored beneath Earth’s surface.

• When magma erupts on or near Earth’s surface, it is called lava or ash.

How do minerals form? (cont.)

• As lava or ash cools above ground or magma cools underground, atoms and ions arrange themselves and form mineral crystals.

• Small crystals form as lava cools quickly on or near Earth’s surface and large crystals sometimes form as magma cools and crystallizes slowly below Earth’s surface.

How do minerals form? (cont.)

• Minerals that form deep within Earth’s crust and mantle are stable under high pressure and high temperature conditions.

• Metamorphic activity can uplift minerals from great depths onto Earth’s surface.

• Changes in pressure and temperature on Earth’s surface combined with agents of erosion can cause minerals to break down and eventually form new minerals.

How do minerals form? (cont.)

• Mineralogists are scientists who study the distribution of minerals, mineral properties, and their uses.

• Scientists use the physical and chemical properties of minerals to learn a mineral’s identity and classify unknown minerals.

Physical Properties

• Color alone cannot be used for mineral identification because many different minerals can be the same color.

• Variations in color reflect the presence of different types of chemical impurities, such as iron, chromium, or manganese.

Physical Properties (cont.)

• The way a mineral reflects or absorbs light at its surface is called luster.

• Minerals that are also metals, such as copper, silver, and gold, reflect light and produce the shiniest luster, called metallic luster.

Physical Properties (cont.)

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• Luster is directly related to the chemical composition of minerals.

• Streak is the color of a mineral in powdered form.

• Streak is only useful for identifying minerals that are softer than porcelain.

• Nonmetallic minerals generally produce a white streak.

Physical Properties (cont.)

• Many metallic minerals produce characteristic streak colors.

• Hardness is the resistance of a mineral to being scratched.

• Friedrich Mohs developed the Mohs’ hardness scale to compare the hardness of different minerals, with scale ranging from 1 to 10.

Physical Properties (cont.)

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• Sometimes the way a mineral breaks provides clues to its identity.

• The arrangement of atoms or ions and the strengths of their chemical bonds determine how a mineral breaks.

• Minerals break where bonds between atoms or ions are weak.

Physical Properties (cont.)

• If a mineral breaks with smooth, flat surfaces, it has cleavage.

Physical Properties (cont.)

• If a mineral breaks and forms uneven surfaces, it has fracture.

• The density of a mineral is also helpful in identifying it. The density of an object is equal to its mass divided by its volume.

• Some minerals have special properties, such as texture, odor, fluorescence, magnetism, or the way they react when they come in contact with hydrochloric acid.

Physical Properties (cont.)

Minerals are valuable resources used to construct many parts of a home.

• Rock that contains high enough concentrations of a desired substance that it can be mined for a profit is called an ore.

• Ores of the elements iron (Fe) and aluminum (Al) are among the most abundant of the metallic mineral resources used every day.

Mineral Resources

• Aluminum is abundant in Earth’s crust but rarely occurs as a native element.

• Gold occurs in a ration of 1 part gold to 4 billion parts rock in Earth’s crust, but in large enough concentrations to be mined for profit.

• The technology industry is dependent upon metallic mineral resources like platinum.

Mineral Resources (cont.)

Humans use nonmetallic minerals that are not ores, such as the raw materials used for road construction, building stone, and fertilizers.

Mineral Resources (cont.)

Construction site: Sascha/Photonica/Getty ImagesLimestone block: Joel Sartore/National Geographic/Getty Images

White gravel: Mark Harwood/Getty ImagesSand: Siede Preis/Getty Images

• A gemstone is a rare and attractive mineral that can be worn as jewelry after it is cut and polished.

Mineral Resources (cont.)

• The physical properties of gemstones also make them useful in industry.

• Sometimes human-made gems are less expensive than the same natural gems.

Mineral Resources (cont.)