Section 4.1: What is a mineral? Section 4.2: Types of Minerals Minerals 4

Objectives Define a mineral. Describe how minerals form. Classify minerals according to their physical and chemical properties. What is a mineral? Section 4.1

Review Vocabulary element: a pure substance that cannot be broken down into simpler substances by chemical or physical means What is a mineral? Minerals are naturally occurring, solid, inorganic compounds or elements. Section 4.1

New Vocabulary mineral crystal luster hardness cleavage fracture streak specific gravity What is a mineral? Section 4.1

Mineral Characteristics Earth’s crust is composed of about 3000 different minerals that play important roles in forming rocks and in shaping Earth’s surface. A mineral is a naturally occurring, inorganic solid, with a specific chemical composition and a definite crystalline structure. What is a mineral? Section 4.1

Mineral Characteristics Minerals are naturally occurring, meaning that they are formed by natural processes. All minerals are inorganic: they are not made from living organisms. Naturally occurring and inorganic What is a mineral? Section 4.1

Mineral Characteristics The atoms in minerals are arranged in regular, repeated, geometric patterns that result in the formation of a crystal. A crystal is a solid in which the atoms are arranged in repeating patterns. Definite crystalline structure What is a mineral? Section 4.1

Minerals are solids and therefore have definite shapes and volumes. Each type of mineral has a chemical composition unique to that mineral. A few minerals are composed of single elements; however, the majority are made from compounds. Solids with specific compositions Mineral Characteristics What is a mineral? Section 4.1

What is a mineral? Section 4.1 In some minerals, such as these varieties of feldspar, chemical composition can vary within a certain range, depending on the temperature at which the mineral crystallizes. Solids with specific compositions Mineral Characteristics

Rock-Forming Minerals What is a mineral? Section 4.1 Eight to ten of the 30 most-common minerals are referred to as rock-forming minerals because they make up most of the rocks in Earth’s crust. Rock-forming minerals are primarily composed of the eight most common elements in Earth’s crust.

Rock-Forming Minerals Minerals from magma What is a mineral? Section 4.1 Molten material that forms and accumulates below Earth’s surface is called magma. Magma is less dense than the surrounding solid rock, so it can rise upward into the cooler layers of Earth’s interior, where it cools and crystallizes.

Rock-Forming Minerals The type and number of elements in the magma determine which minerals will form. The rate at which the magma cools determines the size of the mineral crystals. Small crystals form from rapidly cooling magma, and large crystals form from slowly cooling magma. Minerals from magma What is a mineral? Section 4.1

A liquid is saturated when it becomes full of a dissolved substance and can dissolve no more of that substance. If more of the substance is added to a saturated solution, it is called supersaturated, and mineral crystals form into solids from the solution. What is a mineral? Section 4.1 Rock-Forming Minerals Minerals from solutions

What is a mineral? Section 4.1 Minerals that form from the evaporation of the liquid in which they were dissolved are called evaporites. Rock-Forming Minerals Minerals from solutions

What is a mineral? Section 4.1 Identifying Minerals Geologists identify minerals using tests based on a mineral’s physical and chemical properties, such as crystal form, luster, hardness, cleavage, fracture, streak, color, specific gravity, texture, density, and special properties.

What is a mineral? Section 4.1 Identifying Minerals Crystal form Some minerals form such distinct crystal shapes that they are immediately recognizable. However, perfect crystals are not always formed, so identification based only on crystal form is rare.

What is a mineral? Section 4.1 Identifying Minerals Luster The way that a mineral reflects light from its surface is called luster. There are two types of luster—metallic luster and nonmetallic luster. Luster should usually be used in combination with other physical characteristics to identify a mineral.

What is a mineral? Section 4.1 Identifying Minerals Hardness Hardness is a measure of how easily a mineral can be scratched.

What is a mineral? Section 4.1 German geologist Friedrich Mohs developed a scale by which an unknown mineral’s hardness can be compared to the known hardness of ten easily recognized minerals that, with the exception of diamond, are readily found in nature. Identifying Minerals Hardness

What is a mineral? Section 4.1 Please click the image above to view the interactive table.

What is a mineral? Section 4.1 Identifying Minerals Cleavage and fracture A mineral that splits relatively easily and evenly along one or more planes of weak atomic bonds is said to have cleavage. To identify a mineral based on its cleavage, geologists count the number of cleaved planes and study the angle or angles between them.

What is a mineral? Section 4.1 Minerals that break with rough, arclike, or jagged edges because of their tightly bonded atoms are said to have fracture. Identifying Minerals Cleavage and fracture

What is a mineral? Section 4.1 Streak is the color of a mineral when it is broken up and powdered. Identifying Minerals Streak

What is a mineral? Section 4.1 Identifying Minerals Streak The streak test, which typically involves rubbing the mineral against an unglazed porcelain plate, is most useful in identifying metallic minerals. It can be used only on minerals that are softer than the porcelain plate.

What is a mineral? Section 4.1 Identifying Minerals Color Color is one of the most noticeable characteristics of a mineral. It is also one of the least reliable clues of a mineral’s identity.

What is a mineral? Section 4.1 Identifying Minerals Special properties Several special properties of minerals can also be used for identification purposes. Some of these properties are magnetism, striations, double refraction, effervescence with hydrochloric acid, and fluorescence.

What is a mineral? Section 4.1 Please click the image above to view the interactive table.

What is a mineral? Section 4.1 Identifying Minerals Texture Texture describes how a mineral feels to the touch, and, like luster, it is subjective. It is often used in combination with other tests to identify a mineral.

What is a mineral? Section 4.1 Identifying Minerals Density and specific gravity Two minerals of the same size may have different weights due to a difference in density. Density reflects the atomic mass and structure of a mineral.

What is a mineral? Section 4.1 Identifying Minerals Density and specific gravity Density is expressed as where D = density, M = mass, and V = volume. Because density is not dependent on the size or shape of a mineral, it is a useful identification tool.

What is a mineral? Section 4.1 Identifying Minerals Density and specific gravity The most common measure of density used by geologists is specific gravity, the ratio of the mass of a substance to the mass of an equal volume of water at 4°C.

Objectives Identify different groups of minerals. Illustrate the silica tetrahedron. Discuss how minerals are used. Types of Minerals Section 4.2 Review Vocabulary chemical bond: the force that holds two atoms together

Minerals are classified based on their chemical properties and characteristics. New Vocabulary silicate tetrahedron ore gem Types of Minerals Section 4.2

Mineral Groups In order to study the many minerals on Earth and understand their properties, geologists have classified them into groups. Each group has a distinct chemical nature and specific characteristics. Types of Minerals Section 4.2

Types of Minerals Section 4.2 Mineral Groups Silicates Minerals that contain silicon and oxygen, and usually one or more other elements, are known as silicates. Silicates make up approximately 96 percent of the minerals present in Earth’s crust.

Types of Minerals Section 4.2 Mineral Groups Silicates The basic building block of the silicates is the silica tetrahedron. A tetrahedron (plural, tetrahedra) is a three-dimensional shape that resembles a pyramid.

Types of Minerals Section 4.2 Mineral Groups Silicates Because silicon atoms have four valence electrons, they can bond with four oxygen atoms.

Types of Minerals Section 4.2 Mineral Groups Silicates Individual tetrahedron ions are strong and can bond together to form sheets, chains, and complex three-dimensional structures. The bonds between the atoms help determine several mineral properties, including cleavage or fracture.

Visualizing the Silica Tetrahedron Types of Minerals Section 4.2 The tetrahedron formed by silicates contains four oxygen ions bonded to a central silicon atom. Chains, sheets, and complex structures form as the tetrahedra bond with other tetrahedra. These structures become the numerous silicate minerals that are present on Earth.

Types of Minerals Section 4.2 Please click the image above to view the video.

Mineral Groups Carbonates Carbonates are minerals composed of one or more metallic elements and the carbonate ion CO32–. Types of Minerals Section 4.2 Oxides are compounds of oxygen and a metal, such as hematite (Fe2O3). Oxides

Sulfides are compounds of sulfur and one or more elements, such as pyrite (FeS2). Sulfates are compounds of elements with the sulfate ion (SO42–), such as anhydrite (CaSO4). Mineral Groups Types of Minerals Section 4.2 Other groups

Halides are made up of chloride or fluoride along with calcium, sodium, or potassium, such as halite (NaCl). Native elements are made up of one element only, such as silver (Ag). Mineral Groups Types of Minerals Section 4.2 Other groups

Economic Minerals Minerals are used to make computers, cars, televisions, desks, roads, buildings, jewelry, beds, paints, sports equipment, medicines, and many other things. Types of Minerals Section 4.2

Economic Minerals Ores A mineral is an ore if it contains a useful substance that can be mined at a profit. The classification of a mineral as an ore can change if the supply of or demand for that mineral changes. Types of Minerals Section 4.2

Economic Minerals Ores Ores that are located deep within Earth’s crust are removed by underground mining. Those near Earth’s surface are obtained from large, open-pit mines. The removal of unwanted rock and dirt from mining can be expensive and harmful to the environment. Types of Minerals Section 4.2

Economic Minerals Gems Gems are valuable minerals that are prized for their rarity and beauty. Gems such as rubies, emeralds, and diamonds are cut, polished, and used for jewelry. Types of Minerals Section 4.2

Chapter Resource Menu Section Questions Chapter Assessment Questions Standardized Test Practice Earth Science Online Glencoe Earth Science Transparencies Image Bank Vocabulary Animations Click on a hyperlink to view the corresponding feature. Study Guide Minerals 4

Key Concepts Section 4.1 What is a mineral? Minerals are naturally occurring, solid, inorganic compounds or elements. A mineral is a naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure. A crystal is a solid in which the atoms are arranged in repeating patterns. Study Guide 4

Minerals form from magma or from supersaturated solutions. Minerals can be identified based on their physical and chemical properties. The most reliable way to identify a mineral is by using a combination of several tests. Section 4.1 What is a mineral? 4 Study Guide Key Concepts

Minerals are classified based on their chemical properties and characteristics. In many silicates, one silicon atom bonds with four oxygen ions to form a tetrahedron. Major mineral groups include silicates, carbonates, oxides, sulfides, sulfates, halides, and native elements. Section 4.2 Types of Minerals 4 Study Guide Key Concepts

An ore contains a useful substance that can be mined at a profit. Gems are valuable minerals that are prized for their rarity and beauty. Section 4.2 Types of Minerals 4 Study Guide Key Concepts

All crystalline solids are minerals. a. true b. false 4.1 Section Questions Minerals 4

A mineral can be easily broken into cube-shaped pieces. How many directions of cleavage does this mineral have? a. one b. two c. three d. four 4.1 Section Questions Minerals 4

a. They are relatively large. b. They are relatively small. c. They are well shaped. d. They are all the same mineral. Magma cools and solidifies deep within Earth. What characteristic do the resulting mineral crystals probably have? 4.1 Section Questions Minerals 4

Which group of minerals makes up most of Earth’s crust? a. sulfides b. halides c. oxides d. silicates 4.2 Section Questions Minerals 4

Carbonate minerals form when one or more metals bond with a certain negatively charged ion. Which formula represents this ion? a. CO2– b. CO42– c. CO32– d. CO– 4.2 Section Questions Minerals 4

Gems include diamonds, rubies, and emeralds. What characteristics make gems valuable? 4.2 Section Questions Minerals 4

Possible answer: Gems have many characteristics that make them valuable. Gems have color, clarity, and other optical properties that make them beautiful as cut stones. Most gems also are rare, which increases their value. 4.2 Section Questions Minerals 4

Some hematite has an earthy appearance. Which property of minerals is being described? a. texture b. fracture c. color d. luster Chapter Assessment Questions Minerals 4

Which mineral fizzes when dilute hydrochloric acid is applied to it? a. calcite b. quartz c. gypsum d. pyrite Chapter Assessment Questions Minerals 4

Silicate minerals are built from this basic structural unit. What name is given to the shape this ion forms? a. tetrahedron b. cube c. octahedron d. rhombus Chapter Assessment Questions Minerals 4

Which mineral is a sulfate? a. magnetite (Fe3O4) b. halite (NaCl) c. anhydrite (CaSO4) d. pyrite (FeS2) Chapter Assessment Questions Minerals 4

Which mineral group includes minerals that cannot be broken down chemically? Chapter Assessment Questions Minerals 4 a. halides b. sulfides c. carbonates d. native elements

Which of these solids is a mineral? a. coal b. steel c. volcanic glass d. natural diamond Standardized Test Practice Minerals 4

Which term is used to describe the color of a powdered mineral? a. luster b. streak c. cleavage d. texture Standardized Test Practice Minerals 4

Silica tetrahedra link together to form a variety of mineral structures. How are the tetrahedra bound together in these structures? a. by shared oxygen atoms b. by shared silicon atoms c. by bonds formed with metals d. by bonds formed with water Standardized Test Practice Minerals 4

a. 500 b. 1000 c. 3000 d. 5000 About how many minerals have been identified in Earth’s crust? Standardized Test Practice Minerals 4

Some minerals cleave along smooth planes, but other minerals fracture. What causes minerals to break in these two different ways? Standardized Test Practice Minerals 4

Answer: Minerals cleave, or break along smooth, flat surfaces, when planes of weakness exist within the mineral. These planes of weakness are related to the strength of chemical bonds and structure of the mineral. Minerals that only fracture, or break in irregular ways, do not have significant planes of weakness. Standardized Test Practice Minerals 4

Minerals 4 Glencoe Earth Science Transparencies

Minerals 4 Image Bank

Section 4.1 Vocabulary mineral crystal luster hardness cleavage fracture streak specific gravity Minerals 4

silicate tetrahedron ore gem Section 4.2 Vocabulary Minerals 4

Mohs Scale of Hardness Special Properties of Minerals Visualizing the Silica Tetrahedron Animations 4