Minerals: Building Blocks of Rocks begins with an explanation of the difference between a mineral and a rock, followed by a formal definition of a mineral. Elements, atoms, compounds, ions, and atomic bonding are explained. Also investigated are isotopes and radioactivity. Following descriptions of the properties used in mineral identification, the silicate and nonsilicate mineral groups are examined. The chapter concludes with a discussion of mineral resources, reserves, and ores.
Learning Objectives
After reading, studying, and discussing this chapter, you should be able to:
•Explain the difference between a mineral and a rock.
•Describe the basic structure of an atom and explain how atoms combine.
•List the most important elements that compose Earth’s continental crust.
•Explain isotopes and radioactivity.
•Describe the physical properties of minerals and how they can be used for mineral identification.
•List the basic compositions and structures of the silicate minerals.
•List the economic use of some nonsilicate minerals.
•Distinguish between mineral resources, reserves, and ores.
Chapter Summary
•A mineral is a naturally occurring inorganic solid that possesses a definite chemical structure, which gives it a unique set of physical properties. Most rocks are aggregates composed of two or more minerals.
•The building blocks of minerals are elements. An atom is the smallest particle of matter that still retains the characteristics of an element. Each atom has a nucleus which contains protons and neutrons. Orbiting the nucleus of an atom are electrons. The number of protons in an atom's nucleus determines its atomic number and the name of the element. Atoms bond together to form a compound by either gaining, losing, or sharing electrons with another atom.
•Isotopes are variants of the same element. but with a different mass number (the total number of neutrons plus protons found in an atom‘s nucleus). Some isotopes are unstable and disintegrate naturally through a process called radioactivity.
•The properties of minerals include crystal form, luster, color, streak, hardness, cleavage, fracture, and specific gravity. In addition, a number of special physical and chemical properties (taste, smell, elasticity, malleability, feel, magnetism double refraction, and chemical reaction to hydrochloric acid) are useful in identifying certain minerals. Each mineral has a unique set of properties which can be used for identification
•The eight most abundant elements found in Earth's continental crust (oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium) also compose the majority of minerals.
•The most common mineral group is the silicates. All silicate minerals have the silicon-oxygen tetrahedron as their fundamental building block. In some silicate minerals the tetrahedra are joined in chains; in others, the tetrahedra are arranged into sheets, or three-dimensional networks. Each silicate mineral has a structure and a chemical composition that indicates the conditions under which it was formed.
•The nonsilicate mineral groups include the oxides (e.g., magnetite, mined for iron), sulfides (e.g., sphalerite, mined for zinc), sulfates (e.g., gypsum, used in plaster and frequently found in sedimentary rocks), native elements (e.g., graphite, a dry lubricant), halides (e.g., halite, common salt and frequently found in sedimentary rocks), and carbonates (e.g., calcite, used in portland cement and a major constituent in two well-known rocks: limestone and marble).
•The term ore is used to denote useful metallic minerals, like hematite (mined for iron) and galena (mined for lead), that can be mined for a profit, as well as some nonmetallic minerals, such as fluorite and sulfur, that contain useful substances.