2: Minerals and Rocks
- Page ID
- 20330
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Introduction to Minerals and Rocks
Before we can begin to discuss rocks and the rock materials that make up the state of California, we must address the building blocks of rocks: minerals; and the components that make up minerals: atoms and elements.
Minerals are all around us: the graphite in your pencil, the salt on your table, the plaster on your walls, and the trace amounts of gold (Figure \(\PageIndex{1}\)) in your computer. Minerals can be found in a wide variety of consumer products including paper, medicine, processed foods, cosmetics, electronic devices, and many more. Everything made of metal is also derived from minerals.
A rock is a consolidated aggregate of minerals. By consolidated, we mean hard and strong. A mixture of minerals implies the presence of more than one mineral grain, but not necessarily more than one type of mineral. A rock can be composed of only one type of mineral (e.g., limestone is commonly made up of only calcite), but most rocks are composed of several different minerals. A rock can also include non-minerals, such as fossils or the organic matter within a coal bed.
Rocks are grouped into three main categories based on how they form:
- Igneous: formed from the cooling of magma (molten rock)
- Sedimentary: formed when weathered fragments of other rocks are buried, compressed, and cemented together, or when minerals precipitate directly from solution
- Metamorphic: formed by alteration (due to heat, pressure, and/or chemical action) of a pre-existing rock
This chapter wraps up with a discussion of the distribution of rocks in the state of California, using the Geologic Map of California as our guide.
By the end of this chapter, you should be able to:
- Describe the ways in which atoms bond to form compounds like minerals.
- Differentiate between minerals and rocks.
- Be familiar with the three general rock types, how they form, and how they are related to one another through the rock cycle.
- Describe the general distribution of rock types across the state of California.
- 2.1: Minerals
- Minerals are the building blocks of rocks. This section describes what minerals are and how geologists identify them. It also explains how we categorize minerals in to groups according to their chemical composition.
- 2.2: Mineral Properties
- Geologists use various mineral properties such as streak and hardness to identify them. This section explains those various properties.
- 2.3: The Rock Cycle
- The rock components of the crust are slowly but constantly being changed from one form to another and the processes involved are summarized in the rock cycle. The rock cycle is driven by two forces: (1) Earth’s internal heat engine, which moves material around in the core and the mantle and leads to slow but significant changes within the crust, and (2) the hydrological cycle, which is the movement of water, ice, and air at the surface, and is powered by the sun.
- 2.4: Igneous Rocks
- Igneous rocks form from molten rock. This section describes how igneous rocks form and are classified according to their composition (what they are made of) and their texture (crystal size).
- 2.5: Sedimentary Rocks
- Sedimentary rocks form from sediments: clasts or detritus (bits and pieces of preexisting rock) or from the precipitations of ions out of solution. Sedimentary rocks record what Earth's surface and near-surface environments were like in the past and preserve signs of ancient life in the form of fossils. This section explains how we classify sedimentary rocks and the types of environments in which they form.
- 2.6: Metamorphic Rocks
- Metamorphic rocks are rocks that have undergone change as a result of increased pressure and temperature. This section describes common metamorphic rocks and their parent rocks and the types of environments in which they form. This section also describes serpentinite, California's state rock.
- 2.7: Where the Rocks Are- California's Geologic Map
- California is made up of a wide variety of rock types and geological units (unique, mappable packages of rocks). This section describes the spatial distribution of those rocks with the aid of geologic maps, a product of geological work and a primary tool in a geologist's toolkit.
- 2.8: Chapter Summary
- This page provides a summary of the chapter and key terms.
Thumbnail: A nugget of gold from the California foothills. "Gold nugget (placer gold) (California, USA)" by James St. John via Flickr is licensed under CC BY.