13: Earth Materials
- Page ID
- 55125
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- 13.1: What is Geology?
- This section introduces geology as the study of Earth, including its materials, processes, history, and structure. It explains how geologists use observations of rocks, minerals, landforms, and other evidence to understand how Earth has changed through time. Geology connects processes occurring at Earth’s surface with those operating deep within the planet and provides a foundation for understanding the materials and processes explored throughout this unit.
- 13.2: Minerals and Rocks
- This section introduces minerals and rocks as the basic materials that make up the solid Earth. Minerals are naturally occurring substances with characteristic chemical compositions and structures, while rocks are composed of one or more minerals. Understanding the distinction between minerals and rocks provides a foundation for identifying Earth materials and examining how they form and change.
- 13.3: Mineral Groups
- This section examines how minerals are classified into groups based primarily on their chemical composition. Minerals that contain similar elements or chemical structures often share important characteristics. Organizing minerals into groups makes it easier to understand the large variety of minerals found on Earth and provides a framework for recognizing relationships among common mineral types.
- 13.4: Silicate Minerals
- The vast majority of the minerals that make up the rocks of Earth’s crust are silicate minerals. These include minerals such as quartz, feldspar, mica, amphibole, pyroxene, olivine, and a variety of clay minerals. The building block of all of these minerals is the silica tetrahedron, a combination of four oxygen atoms and one silicon atom. As we’ve seen, it’s called a tetrahedron because planes drawn through the oxygen atoms form a shape with 4 surfaces.
- 13.5: Mineral Properties
- This section examines the physical properties used to identify minerals. Characteristics such as color, streak, luster, hardness, cleavage, fracture, and density can be observed or measured to distinguish one mineral from another. Because individual properties are not always unique to a particular mineral, geologists typically use several properties together when making an identification.
Chapter 13: Earth Materials — Introduction
With this chapter, we begin our study of geology and shift our attention from the atmosphere above us to the solid Earth beneath our feet. Geology examines the materials that make up Earth, the processes that shape it, and the evidence those materials preserve about our planet's history. Before we can understand processes such as volcanism, mountain building, or plate tectonics, we first need to become familiar with the basic materials from which the solid Earth is constructed.
We begin by distinguishing between minerals and rocks. Minerals are the fundamental building blocks of rocks, and their chemical composition and internal structure give them characteristic physical properties. Although thousands of minerals are known, they can be organized into groups based on their composition, and a relatively small number account for much of Earth's crust. In particular, silicate minerals are especially important because of the abundance of silicon and oxygen in the crust.
Finally, we will examine the physical properties geologists use to identify minerals. Properties such as hardness, luster, streak, cleavage, and fracture provide observable evidence that can be used to distinguish one mineral from another. These identification skills provide a foundation for the next chapter, where we will move from individual minerals to rocks and use those materials to begin reconstructing Earth's history.