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Earth Science, 12e Minerals: Building Blocks of Rocks Chapter 2

Minerals: the building blocks of rocks  Definition of a mineral Natural Inorganic Solid Possess an orderly internal structure of atoms Have a definite chemical composition  Mineraloid – lacks an orderly internal structure

Composition and structure of minerals  Elements Basic building blocks of minerals Over 100 are known  Atoms Smallest particles of matter Have all the characteristics of an element

Periodic Table of the Elements Periodic Table of the Elements Figure 2.4

How atoms are constructed  Nucleus – central part of an atom that contains Protons – positive electrical charges Neutrons – neutral electrical charges  Energy levels, or shells Surround nucleus Contain electrons – negative electrical charges

Simplified view of the atom Figure 2.5

How atoms are constructed  Atomic number is the number of protons in an atom’s nucleus  Bonding of atoms Forms a compound with two or more elements Ions are atoms that gain or lose electrons  Isotopes Have varying number of neutrons

How atoms are constructed  Isotopes Have different mass numbers – the sum of the neutrons plus protons Many isotopes are radioactive and emit energy and particles

Minerals  Physical properties of minerals Habit Luster Color Streak Hardness Cleavage

The mineral quartz often exhibits good crystal shape Figure 2.21

Pyrite (fool’s gold) displays metallic luster Figure 2.11

Figure 2.13 Mohs scale of hardness

Three examples of cleavage – halite, calcite, and fluorite Figure 2.15 B

Minerals  Physical properties of minerals Fracture Specific gravity Other properties Taste Smell Elasticity Malleability

Conchoidal fracture Conchoidal fracture Figure 2.16

Minerals  Physical properties of minerals Other properties Feel Magnetism Double refraction Reaction to hydrochloric acid

Minerals  A few dozen minerals are called the rock- forming minerals The eight elements that compose most rock- forming minerals are oxygen (O), silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K), and magnesium (Mg) Most abundant atoms in Earth’s crust are oxygen (46.6% by weight) and silicon (27.7% by weight)

Composition of continental crust Figure 2.19

Minerals  Mineral groups Rock-forming silicates Most common mineral group Contain the silicon-oxygen tetrahedron (molecule) Four oxygen atoms surrounding a much smaller silicon atom Combines with other atoms to form the various silicate structures

The silicate (SiO 4 ) 4– molecule Figure 2.20

Minerals  Mineral groups Rock-forming silicates Groups based on tetrahedral arrangement Olivine – independent tetrahedra Pyroxene group – tetrahedra are arranged in chains Amphibole group – tetrahedra are arranged in double chains

Hornblende – a member of the amphibole group Hornblende – a member of the amphibole group Figure 2.21

Minerals  Mineral groups Rock-forming silicates Groups based on tetrahedral arrangement Micas – tetrahedra are arranged in sheets Two types of mica are biotite (dark) and muscovite (light) Feldspars – Three-dimensional network of tetrahedra

Minerals  Mineral groups Rock-forming silicates Groups based on tetrahedral arrangement Feldspars Two types of feldspar are Orthoclase and Plagioclase Quartz – three-dimensional network of tetrahedra

Potassium feldspar Potassium feldspar Figure 2.21

Minerals  Mineral groups Rock-forming silicates Feldspars are the most plentiful mineral group Crystallize from molten material Nonsilicate minerals Major groups Oxides Sulfides

Minerals  Mineral groups Nonsilicate minerals Major groups Sulfates Carbonates “Native” elements

Common nonsilicate mineral groups Common nonsilicate mineral groups Table 2.1

Minerals  Mineral groups Nonsilicate minerals Carbonates A major rock-forming group Found in the rocks limestone and marble Halite and gypsum are found in sedimentary rocks Many have economic value

Minerals  Mineral resources Reserves are already identified deposits Ores are useful metallic minerals that can be mined at a profit Economic factors may change and influence a resource

An underground halite (salt) mine Figure 2.22

End of Chapter 2