Chapter 2: Earth Materials

Elements and Compounds• Element

– Most fundamental substance into which matter can be separated by chemical means

• Atom– Smallest single particle that keeps

element’s distinct chemical properties

– Protons (+)– Neutrons (neutral)– Electrons (-)– Net atom charge

• Protons (+) + electrons (-)

Elements and Compounds• Atomic number

– # of protons• Atomic mass

– # of protons + # of neutrons

• Isotopes– Atoms with same

atomic # but different mass #

Elements & Compounds• Electron (-)

– Electron “shells”– Ion

– Cation (+)– Anion (-)

Compounds, molecules and bonding• Compound

– Combo of atoms from 1 or more elements in specific ratio

• Molecule– Smallest unit with all properties

of a specific compound• Bond

– Force that holds together atoms in molecules &/or compounds

Compounds, molecules & bonding• Ionic Bonding

– 1 atom transfers electron to another

• Gain or lose electrons– I.e. = Table salt (sodium

chloride or NaCl)

Compounds, molecules and bonding• Covalent Bond

– Electrons from different atoms “pair up” & create bond

• Share electrons– Strongest of chemical bonds

Compounds, molecules and bonding• Metallic Bond

– Electrons shared among several atoms

• Outer electrons drift between atoms

– Good conductors of heat & electricity

Compounds, molecules and bonding• Van der Waals Bond

– Attraction between electrically neutral molecules with asymmetrical charge

• Dipolar molecules• Weak bonds• I.e. Water

What Is a Mineral?• Mineral

– Naturally formed– Solid– Inorganic – Specific crystal structure – Specific chemical composition

Composition of minerals• Atomic substitution

– Elements with similar size & charge can substitute for each other

• Crystal structure– Atoms/molecules arranged

into regular patterns

– Mineraloid• Polymorphs

– Same chemical composition but different crystal structure

Telling minerals apart• Luster

– Quality & intensity of light reflection• Metallic• Non-metallic

– Vitreous– Resinous– Pearly

Telling minerals apart• Crystal form

– Any flat or planar surface that forms during mineral growth

• Habit– Particular mineral’s

distinctive shape

Telling minerals apart• Hardness

– Mineral’s resistance to scratching

– Mohs scale (1-10)

Talc

Fluorite

Calcite

Gypsum

Topaz

Corundum

Diamond

Quartz

Feldspar

Apatite

1

2

3

4

5

6

7

8

9

10

Mineral Hardness Image Common Objects Reference

Fingernail (2.5)

Copper Penny (3.5)

Wire Nail (4.5)

Glass (5.5)

Streak Plate (6.5)

Telling minerals apart• Cleavage

– Mineral breaks in a regular pattern

– Relates to crystal structure within mineral

Telling minerals apart• Color

– Least reliable• Light absorbed by mineral

• Streak– Powdered trace of mineral made by rubbing specimen

across unglazed porcelain piece

Telling minerals apart• Density

– Mass / volume– Compactness

of atoms• Other mineral properties

– Birefringent• Double images

– Effervescence• Fizzes in acid

– Magnetic• Attracted to magnet

– Luminescence or fluorescence

• UV “glow”

Mineral families & their uses• Minerals of Earth’s crust

– Silicate minerals• Minerals contain both silicon & oxygen

– Silicon-oxygen tetrahedron• 1 Si atom bonded to 4 O atoms

Mineral families & resources• Other minerals of

Earth’s crust– Oxides– Carbonates

• Ore deposits– Localized concentration

that can be extracted profitably

Rocks: A First Look• Rock

– Naturally formed aggregate of minerals & possibly other non-mineral matter

– Record history of Earth processes

Granite

Quartz

Feldspar

Biotite

Rocks: A First Look• Igneous

– Form by cooling & solidification of molten rock• Magma

• Sedimentary– Form under conditions of

low pressure & low temperature near the surface

• Metamorphic– Altered by exposure to high

temperature, high pressure or both