GeoLOGY 100 Lecture Outline -

Geochemistry and Minerals (Ch 3)

 

I. Lecture Content - Topics

Matter and Its Physical States

Elements, Atoms, and Isotopes

Chemical Bonding and Compounds

Crystals and Minerals

Defining a Mineral

Classification of Minerals

The Silicate Mineral Group

The Carbonate Mineral Group

Other Mineral Groups

Mineral Identification

Focus on The Major Rock-Forming Minerals

Mineral Resources and Reserves

 

II. Physical States of Matter

A. Definition of Matter

1. Anything that has mass and occupies space

      Atoms and molecules

      All Earth materials

2. The intimate relationship between matter and energy

      Einstein's famous equation - E = mc2

 

B. The Four Different States of Matter

1. Solid

2. Liquid

3. Gas

4. Plasma

 

C. Transformation of Matter from One State to Another

1. Also called a "phase change"

 

2. Always involves a condition change in the system

 

3. Change in physical state always involves a process

 

4. Many major Earth processes involves a phase change

 

III. Elements, Atoms and Isotopes

A. Elements: Basic Building Blocks of Earth Materials

1. There are 92 naturally occurring elements on Earth

       Most created in (an) ancient star(s)

       Each element has a name and a symbol

       Organized in the Periodic Table of Elements

       Range in mass from Hydrogen to Uranium

 

2. Most Common Elements in Earth's Crust

    Oxygen (63%)

    Silicon (28%)

    Aluminum (8%)

    Iron (5%)

    Calcium (4%)

    Sodium (3%)

    Potassium (3%)

    Magnesium (2%)

 

2. Elements are composed of tiny particles called atoms

       Smallest units of matter that characterize elements

       Atoms are composed of even smaller particles

 

3. Atoms have an organized internal structure

       Center of atom consists of nucleus (positively-charges protons and neutral neutrons)

 

       Outer part of atoms consists of a "cloud" of negatively-charged electrons

 

4. Number of protons in an atom = the type of element

      Called the atomic number

5. The sum of protons and neutrons in an atom determines

the element's atomic mass

 

      Called the atomic mass number

 

6. Atoms of a single element can vary in atomic mass

      Proton # same; Variation in neutron #

      Called "isotopes"

      Most isotopes are stable; some are unstable

 

 

IV. Chemical Bonding, Molecules & Compounds

A. Bonding of Atoms into Molecules & Compounds

1. Molecule defined: A substance made up of two or more

atoms that are bonded together

 

2. Compound defined: A substance made up of atoms from

two or more elements that are bonded together

 

3. Ions defined: are atoms, molecules, or compounds that

have either, more, or less electrons (-) than the

number of protons (+)

 

       Ions possess an electrical charge (+ or -)

       Compounds that are ions are called radicals

 

4. Bonding defined: The process of joining together two

or more atoms into molecules or compounds

 

5. Bonding is caused by the interaction of the electron

clouds between closely adjoining atoms and/or

molecules

 

5. Two major types of chemical bonding

      Ionic

      Covalent

 

6. Two other types of chemical bonding

      Metallic

      Van der Waal

 

B. Ionic Bonding

1. The formation of a compound by the electromagnetic

attraction of oppositely-charged ionic substances

      Involves the transfer of electron(s)

      Example: Halite (sodium chloride)

 

2. Neutral ionic compounds are called salts and consist of

a pair of ions

      Cation (positively-charged ion)

      Anion (negatively-charged ion)

 

3. Ionic bonds are relatively weak (easily broken)

 

C. Covalent Bonding

1. The formation of a molecule or compound by the sharing

of the outermost electrons between atoms

 

      Examples:

    Diamond (C-pure carbon)

    Silica radical (SiO4)-4

    Carbonate radical (CaCO3)-2

 

2. Covalent bonds are relatively strong compared to ionic

 

3. Minerals consist of compounds that typically have both

ionic and covalent bonds

 

V. Crystals and Minerals

A. Crystalline Substances

1. Crystals are highly-ordered, solid substances having a

regular, three-dimensional framework

 

      Ordered internal atomic arrangement

      Unit structures are of atomic scale

 

2. When completely unimpeded, crystals will grow with into

perfect geometric forms, that reflect their unit structure

 

3. Not all solid, rigid substances are crystalline

 

      Called amorphous - lack crystal structure

      Examples are glass, obsidian & opal

B. Mineral - Defined

 

1. Naturally occurring

2. Inorganic

3. Crystalline solid

4. Narrowly defined chemical composition

5. Characteristic physical properties

 

C. Over 3,500 Different Minerals Have Been Recognized

 

 

VI. Classification of Minerals into Groups

A. The Silicate Group

1. Characteristics of the Silicate Group

      Base compound is the silica radical (SiO4-4)

      Basic structure is the silica tetrahedron

      Vast majority of rock-forming minerals found in the crust and mantle belong to the silicate group

 

2. The Silicate Group has several subgroups that are based

on their arrangement of silica tetrahedral:

 

      Olivine Group

      Pyroxene Group

      Amphibole Group

      Mica Group

      Clay Mineral Group

      Quartz Group

 

3. The Silicate Group can also be divided into two groups

based on chemical composition

 

      The Ferromagnesian Silicates

    Olivine

    Pyroxenes

    Amphiboles

    Dark-colored Micas

 

      The Nonferromagnesian Silicates

    Quartz

    Plagioclase feldspar

    Potassium feldspar

    "White" micas

 

4. Silicate group minerals form primarily in igneous and

metamorphic rocks, but are also present as detritus

in sedimentary rock and sediments.

 

5. Hand samples of the different silicate subgroups:

 

B. The Carbonate Group

1. Characteristics of the Carbonate Group

      Base compound is carbonate radical (CaCO3)-2

      Carbonate minerals are restricted to the crust

 

2. Carbonate minerals form mainly form in sedimentary

and metamorphic rocks

 

3. Most typical carbonate minerals are calcite, aragonite,

and dolomite.

 

4. Hand samples of carbonate minerals

D. Other Mineral Groups

1. The Oxide Group

2. The Sulphide Group

3. The Halide Group

4. The Sulphate Group

 

VII. Identification of Minerals

A. Physical and Chemical Properties of Minerals

 

1. Luster & Color

2. Cleavage & Fracture

3. Hardness

4. Crystal Form

5. Density (specific gravity)

6. Reaction to acid

7. Magnetic susceptibility

8. Reaction to ultraviolet light

9. Radioactivity

10. Taste

 

B. Optical Properties of Minerals

1. Refraction of polarized light through minerals

       Each mineral has a unique light refraction value

       Based on both crystal structure & composition

 

C. Atomic Properties of Minerals

1. Interaction of X-rays and mineral crystals

       Each mineral has a unique X-ray pattern

       Based on both crystal structure & composition

 

D. Techniques Used for Identifying Minerals

1. Hand sample (bare eye) identification

2. "Blowpipe" flame-jet technique

3. Polarizing microscope

4. Atomic absorption

5. Electron-beam microprobe

6. X-ray diffraction or fluorescence

7. Nuclear (neutron activation)

 

VIII. The Major Rock-Forming Minerals

A. Rock defined:

1. An aggregate of crystals consisting of one or more

mineral species

 

2. Two exceptions are obsidian (natural glass) and coal

 

B. Only About a Dozen Major Rock-Forming Minerals

Form the Bulk of Earth's Lithosphere

 

Ferromagnesian Silicates (mainly igneous & metamorphic)

 

1. Olivine - (Mg, Fe)2SiO4

 

2. Pyroxene group - Ca, Mg, Fe, Al-silicate

      Augite species most common

 

3. Amphibole group - hydrous Na, Ca, Mg, Fe, Al-silicate

      Hornblende species most common

 

4. Biotite - hydrous K, Mg, Fe, Al-silicate

 

Nonferromagnesian Silicates (all three rock types)

 

5. Quartz - SiO4

 

6. Potassium feldspar - KalSi3O8

      Orthoclase & Microcline most common

 

7. Plagioclase feldspar group -

      Varies from CaAl2Si2O8 to NaAlSi3O8

 

8. Muscovite - hydrous K, Al silicate

 

9. Clay group - variable hydrous Al silicate

 

Carbonates (sedimentary & metamorphic rocks)

 

10. Calcite - CaCO3

 

11. Dolomite - CaMg(CO3) 2

 

Sulphates (exclusively sedimentary rocks)

 

12. Anhydrate - CaSO4

 

13. Gypsum - CaSO4 . 2H2O

 

Halides (exclusively sedimentary rocks)

 

14. Halite - NaCl

 

 

IX. Mineral Resources and Reserves

A. Resource & Reserve defined by the U.S.G.S

1. Resource:

A concentration of naturally occurring solid, liquid,

or gaseous material in or on the Earth's crust in such

a form and amount that economic extraction of a

commodity from the concentration is currently or

potentially feasible.

 

2. Reserve:

That part of a resource base that can be currently economically extracted (given today's market price)

 

B. Factors That Define a Resource From a Reserve

1. Total abundance of mineral

2. Degree of concentration of a mineral

3. Geographic location

4. Political location

5. Market commodity price

6. Technological expertise

7. New markets and uses

 

C. Nonfuel Mineral Production in the United States

1. Compare Figures in Table 2.8

 

2. About $40 billion in mineral commodities extracted

from U.S. mines

 

3. The major mineral commodities extracted in the U.S

      Sand and gravel

      Cement

      Crushed stone

      Gold

      Copper

      Silver

      Iron ore

      Lead

      Magnesium metal

      Boron

      Phosphate rock

      Clays

 

D. Interesting Fact about Metal Resources

      About 75% of all metals mined in the world come

from about only 150 locations

 

E. Mineral Resources are Nonrenewable

      World's richest deposits have already been mined

 

X. Vocabulary Terms

Amphibole

Atom

Atomic mass number

Atomic number

Biotite

Bonding

Calcite

Carbonate mineral

Cleavage

Compound

Covalent bond

Crystalline solid

Dolomite

Electron

Electron cloud

Element

Ferromagnesian silicate

Gypsum

Halide

Hardness

Ion

Ionic bond

Luster

Mineral

Muscovite

Native element

Neutron

Nonferromagnesian silicate

Nucleus

Olivine

Potassium feldspar

Plagioclase feldspar

Proton

Pyroxene

Quartz

Reserve

Resource

Rock

Rock-forming mineral

Silica

Silica tetrahedron

Silicate