GEOL: CHAPTER 3 Minerals: The Building Blocks of Rocks

GEOL: CHAPTER 3

Minerals: The Building Blocks of Rocks

Cluster of crocoite crystals, a rare and brightly colored lead chromate mineral (Smithsonian Museum).

LO1: Define matterLO2: Explore the world of mineralsLO3: Identify mineral groups recognized by

geologistsLO4: Identify physical properties of mineralsLO5: Recognize rock-forming mineralsLO6: Explain how minerals formLO7: Recognize natural resources and

reserves

Learning Outcomes

• Naturally occurring

• Inorganic*

• Crystalline solid

• Narrowly defined chemical composition

• Characteristic physical properties

Mineral Definition

• Fertilizers

• Feed supplements

• Economic well-being

• Affects foreign relations

• Building blocks of rocks

Minerals Are Important

• Liquid

• Gas

• Solid

• Plasma

Four States of Matter

• Comprise elements

• Nucleus with protons and neutrons

• Electrons in electron shells

• Atomic number– Number of protons

• Atomic mass number– Isotopes

Atoms

Fig. 3-3, p. 49

Stepped Art

6 p8 n

14C (Carbon 14)13C (Carbon 13)

6 p7 n

Nucleus

6 p6 n

12C (Carbon 12)

Isotopes of an atom have a different number of neutrons…

• Ionic bonds

• Covalent bonds

• Metallic bonds

• Van der Waals bonds

Types of Bonds

• Transfer of electrons

• Electron shell completion

• Ions either positive or negative

• Opposite charges attract

• Ionic compounds

Ionic Bonding

Fig. 3-4a, p. 50

Stepped Art

Sodiumatom11 p+ 11 e–

Sodiumion

11 p+ 10 e–

+

Chlorineion

17 p+ 18 e–

–

electron transfer

Chlorineatom17 p+ 17 e–

• Sharing of electrons

• Electron shell completion

• Electron shells overlap

• Carbon needs 4 electrons, so forms four covalent bonds

• Silicates: Silicon bonds with oxygen are part covalent, part ionic

Covalent Bonding

• Electrons in some metals are mobile and shift from one atom to another

• Metallic luster

• Good conductors of electricity and heat

• Easily reshaped

Metallic Bonding

• Electrically neutral atoms and molecules

• Weak attractive forces

• Graphite and pencils

Van der Waals Bonding

• Inorganic

• Naturally occurring

• Crystalline solid

• Narrowly defined chemical composition

• Characteristic physical properties

Mineral Definition

• Crystals have regular geometric shape– Planar surfaces/crystal faces– Sharp corners– Straight edges

• Cleavage

• Constancy of interfacial angles

Mineral Crystals

A few varieties of crystalline forms

Common elements in Earth’s crust

• 3500+ minerals

• 2 dozen common minerals

• Mineral groups share same negatively charged ion or radical

Mineral Groups

• Silicon and oxygen are common elements

• 95% of Earth’s crust

• Silica tetrahedra– Chains– Continuous sheets– Three-dimensional networks

Silicate Minerals

• Contain iron (Fe), Magnesium (Mg), or both

• Usually dark• Dense• Olivine• Pyroxenes• Amphiboles• Biotite

Ferromagnesian Silicates

• No iron or magnesium

• Lighter colored

• Less dense

• Potassium feldspars

• Plagioclase feldspars

• Quartz

Nonferromagnesian Silicates

• Carbonate radical (CO3)-2

• Calcium carbonate, calcite, aragonite

• Limestone

• Dolomite

Carbonate Minerals

• Oxides

• Native elements

• Phosphates

• Sulfates

• Sulfides

• Halides

Other Mineral Groups

• Luster– Quality and intensity of light reflected from

surface

• Color

• Crystal form– Number of sides– Different minerals can have the same form

Physical Properties of Minerals

• Cleavage– Quality– Direction– Angles of intersection

• Fracture– Breakage along irregular surfaces

Physical Properties of Minerals, cont.

Several Types of Mineral Cleavage.

Cross section

Fig. 3-15, p. 60

Stepped ArtHornblende crystal and cross sectionof crystal showing cleavage.

Cross section

Augite crystal and cross sectionof crystal showing cleavage.

124°56°

93°87°

• Hardness

• Specific gravity– Ratio of mineral weight to equal volume of

water at 4ºC

• Feel

• Taste

Physical Properties of Minerals, cont.

Mohs scale of

hardness

talc

apatite

corundum

• Magnetic or not

• Plasticity: ability to bend

• Double refraction

• Chemical tests: acid on calcite

Physical Properties of Minerals, cont.

1. Cooling of magma2. Cooling of lava3. Combination of minerals in seawater or

lakes4. Organisms construct carbonate shells5. Chemical processes change composition

or mineral structure6. Metamorphism: heat, pressure,

chemically active fluids

How Minerals Form

• Natural resource: form and concentration that is economically feasible– Minerals– Rocks– Liquid petroleum– Natural gas

Natural Resources

• Part of resource that is known and can be recovered at economically feasible cost

• What makes a reserve a resource:– Transportation costs– Labor costs– Market price– Technology changes

Reserves