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
- The definition of a mineral encompasses five key characteristics: it must be naturally occurring, inorganic, solid at room temperature, have a regular internal structure, and a defined chemical composition. Minerals are formed by atoms arranged in a crystal lattice and can include elements such as sodium and chlorine forming halite. Minerals are categorized based on their chemical compositions, such as oxides, sulfides, carbonates, and silicates.
- 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
- This page details the formation and classification of igneous rocks. Igneous rocks form from cooling magma, either extrusively at or near the Earth's surface or intrusively within the crust. Bowen's reaction series describes the order of mineral crystallization in cooling magma. The composition of the magma (mafic, intermediate, and felsic) influences which minerals form.
- 2.5: Sedimentary Rocks
- This page provides a detailed overview of clastic (detrital) sedimentary rocks, which are formed from the accumulation of rock and mineral fragments transported by natural forces and deposited as sediment. It explains the classification of clastic sedimentary rocks based on clast size, roundness, and sorting. The page also touches on other types of sedimentary rocks, including chemical and biochemical sedimentary rocks like limestone and chert.
- 2.6: Metamorphic Rocks
- Metamorphic rocks form through the transformation of pre-existing rocks under heat and pressure, resulting in new minerals or larger crystals. This process often occurs during mountain-building and plate convergence, leading to foliated rocks with aligned mineral bands. Non-foliated metamorphic rocks like quartzite and marble form under similar pressures without alignment. The text highlights serpentinite, California's state rock, known for its mineral serpentine.
- 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
- The page provides an overview of minerals and their properties, including their chemical compositions and types of bonding, as well as a description of the rock cycle and its three main types: igneous, sedimentary, and metamorphic. It also details the formation and identification of igneous rocks, sedimentary rocks, and mentions the presence of geological maps, with an emphasis on California's geological features.
- 2.9: Detailed Figure Descriptions
- Detailed text descriptions of complex figures in this chapter.
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.