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
Mineral
Telling minerals
apart
• Hardness
– Mineral’s resistance to
scratching
– Mohs scale (1-10)
Hardness
Talc
1
Gypsum
2
Image
Common
Objects
Reference
Fingernail
(2.5)
Calcite
3
Copper
Penny (3.5)
Fluorite
4
Wire Nail
(4.5)
Apatite
5
Glass (5.5)
Feldspar
6
Streak Plate
(6.5)
Quartz
7
Topaz
8
Corundum
9
Diamond
10
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
Biotite
Feldspar
– Naturally formed
aggregate of minerals &
possibly other nonmineral matter
– Record history of Earth
processes
Granite
Quartz
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