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

Earth Science, Earth Science, 12e12e

Minerals: Building Minerals: Building Blocks of RocksBlocks of Rocks

Chapter 2Chapter 2

Minerals: the building Minerals: the building blocks of rocks 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 Composition and structure of minerals 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 Periodic Table of the ElementsElements

Figure 2.4

How atoms are constructed 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 atomSimplified view of the atom

Figure 2.5

How atoms are constructed 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 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 Minerals

Physical properties of minerals • Habit• Luster• Color• Streak• Hardness• Cleavage

The mineral quartz often The mineral quartz often exhibits good crystal shapeexhibits good crystal shape

Figure 2.21

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

Figure 2.11

Figure 2.13

Mohs scale of hardness

Three examples of cleavage –Three examples of cleavage –halite, calcite, and fluoritehalite, calcite, and fluorite

Figure 2.15 B

Minerals Minerals

Physical properties of minerals • Fracture• Specific gravity• Other properties

• Taste• Smell• Elasticity• Malleability

Conchoidal fractureConchoidal fracture

Figure 2.16

Minerals Minerals

Physical properties of minerals • Other properties

• Feel• Magnetism• Double refraction• Reaction to hydrochloric acid

Minerals 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 Composition of continental crustcontinental crust

Figure 2.19

Minerals 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 (SiOThe silicate (SiO44))4–4–

moleculemolecule

Figure 2.20

Minerals 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 Hornblende – a member of the amphibole groupthe amphibole group

Figure 2.21

Minerals 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 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 feldsparPotassium feldspar

Figure 2.21

Minerals Minerals

Mineral groups • Rock-forming silicates

• Feldspars are the most plentiful mineral group • Crystallize from molten material

• Nonsilicate minerals • Major groups

• Oxides• Sulfides

Minerals Minerals

Mineral groups • Nonsilicate minerals

• Major groups• Sulfates• Carbonates• “Native” elements

Common nonsilicate Common nonsilicate mineral groupsmineral groups

Table 2.1

Minerals 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 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 An underground halite (salt) minehalite (salt) mine

Figure 2.22