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Minerals
Composition of the Sun
Composition of the Sun
• Abundance of Light
Elements
• Rarity of Lithium,
Beryllium, Boron
• Preference for Even
Numbers
• Abundance peak at
Iron, trailing off after
How Elements Form in Stars
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Sun: 4 H  He
He + particle  Mass 5 – Unstable
He + He  Mass 8 – Unstable
He + He + He  C
Add more He to make heavier elements
End of the line is iron for energy production
Atoms beyond Iron made in massive stars
What are Planets Made of?
• Same material as Sun
• Minus the elements that remain mostly in
gases
• We find this pattern in a certain class of
meteorites
Chondrites
The Earth’s Crust looks Very
Different
Composition of the Crust
Minerals are the Chemicals that
make up the Earth
• NATURALLY-OCCURRING
• INORGANIC
• CHEMICAL COMPOUNDS
• ABOUT 3000 KNOWN
• 200 COMMON
• 20 ROCK-FORMING
Atomic Bonding
1. IONS
Atomic Bonding
2. ELECTRICAL NEUTRALITY
• (+) and (-) Cancel Out
3. BONDING (SATISFY 1 & 2)
• Ionic (NaCl)
• Covalent (O2)
• Metallic (Cu, Al, Fe)
• Hydrogen (in water)
Ionic and Covalent Bonding
Metallic Bonding
Hydrogen Bonding
Summary of Bonding
• Ionic bonding holds rocks and minerals
together
• Covalent bonding holds people and other
organisms together
• Metallic bonding holds civilization together
• Hydrogen bonding gives water its heatretaining and solvent properties
4. Lattices
• Atoms in crystals form a repeating pattern
called a Lattice
5. Radicals
• Many minerals contain groups of atoms that
behave as single units
NAMING MINERALS
COLOR
• Glauconite (Greek: Glaucos = Blue-green)
OTHER PROPERTIES, USES
• Magnetite
COMPONENTS
• Chromite
PLACES
• Muscovite (Moscow)
PEOPLE
• Biotite
CHEMICALS (AND
MINERALS) ARE CLASSIFIED
BY THEIR ANIONS
For Example: Iron Compounds
Have Little in Common
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Fe: Gray, Metallic
FeCl2: Light Green, Water Soluble
FeSO4: Light Green, Water Soluble
FeCO3: Brown, Fizzes in Acid
FeS2: Dense, Brittle, Metallic, Cubic
Crystals
On the Other Hand, Sulfides have
Many Properties in Common
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FeS2
CuFeS2
PbS
ZnS2
All are Dense, Brittle, Metallic, have Cubic
Crystals
Identifying
Minerals
IDENTIFYING MINERALS
COLOR -Sometimes Distinctive
• Often Unreliable
• Affected By:
–
–
–
–
Chemical Impurities
Surface Coating
Grain Size
Weathering
IDENTIFYING MINERALS
(Continued)
HARDNESS
• Resistance to Scratching
• Directly related to relative strength of
atomic bonds
• Scratch Test (Mohs)
• Indentation Test (Knoop)
Common Errors due to:
• Weathering, ‘Chalk' marks
• Breaking vs. Scratching
Mohs vs. Knoop Scales
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Talc:
Gypsum, Fingernail:
Calcite, Penny:
Fluorite:
Apatite:
Feldspar, Glass:
Quartz:
Topaz:
Corundum:
Diamond:
very small
30
135
163
430
560
820
1340
2100
7000
IDENTIFYING MINERALS
(Continued)
DENSITY
• Directly related to masses of component
atoms and their spacing
• Usually very consistent
DENSITY - gm/cm3
(weight relative to water )
• Air:
0.001
Wood - Balsa: 0.1, Pine: 0.5, Oak: 0.6-0.9
Gasoline: 0.7, Motor Oil: 0.9
Ice:
0.92
Water:
1.00
Sugar:
1.59
Halite:
2.18
Quartz:
2.65
Most Major Minerals: 2.6-3.0
Aluminum: 2.7
DENSITY
• Pyrite, Hematite, Magnetite: 5.0
Galena:
7.5
Iron:
7.9
Copper:
9
Lead:
11.4
Mercury:
13.6
Uranium:
19
Gold:
19.3
Platinum:
21.4
Iridium: 22.4 (densest material on Earth)
IDENTIFYING MINERALS
(Continued)
LUSTER
• Metallic or Nonmetallic is the most
important distinction.
• Resinous, waxy, silky, etc. are selfexplanatory.
• Vitreous is often used for glassy luster.
IDENTIFYING MINERALS
(Continued)
CLEAVAGE
• Tendency to split along smooth planes between
atoms in crystal
• Thus directly related to atomic structure
• Related to Crystal Form
• Every cleavage face is a possible crystal face
• Not every crystal face is a cleavage face.
Quartz commonly forms crystals but lacks
cleavage.
IDENTIFYING MINERALS
(Continued)
CRYSTAL FORM
• Takes Luck & Practice
• Well-formed crystals are uncommon
• Crystal Classification is somewhat subtle
FRACTURE
IDENTIFYING MINERALS
(Continued)
GEOLOGIC SETTING
• Some minerals occur in all geologic
settings: quartz, feldspar, pyrite
• Some minerals occur mostly in sedimentary
settings: calcite, dolomite
• Some minerals occur mostly in igneous
settings: olivine
• Some minerals occur mostly in
metamorphic settings: garnet, kyanite
IDENTIFYING MINERALS
(Continued)
SPECIAL PROPERTIES
• Taste, Magnetism, Etc.
EXPERIENCE AND READING
PROFESSIONAL METHODS
• Chemical Analysis
• X-Ray Studies
• Thin Section
Diffraction
Diffraction
MAJOR MINERAL SUITES
ELEMENTS
Metallic:Au, Ag, Cu
• Not Al, Pb, Zn, Fe, etc.
Nonmetallic: C - Diamond, Graphite
• Sulfur
MAJOR MINERAL SUITES
SULFIDES: Dense, Usually Metallic
Many Major Ores
• Pyrite FeS2
• Chalcopyrite CuFeS2
• Galena PbS
• Sphalerite ZnS2
• Molybdenite MoS2
MAJOR MINERAL SUITES
HALIDES: Usually Soft, Often Soluble
• Halite NaCl
• Fluorite CaF2
SULFATES: Soft, Light Color
• Gypsum CaSO4
• Barite BaSO4
MAJOR MINERAL SUITES
OXIDES: Often Variable, Some Ores
• Hematite Fe2O3
• Bauxite Al(OH) 3 (a hydroxide)
• Corundum Al2O3 (Ruby, Sapphire)
CARBONATES: Fizz in Acid, Give off CO2
• Calcite CaCO3
• Dolomite CaMg (CO3)2
MOST IMPORTANT MINERAL
SUITE:
The Silicate Minerals
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Si + O = 75% of Crust
Silicates make up 95% + of all Rocks
SiO4: -4 charge
Link Corner-To-Corner by Sharing Oxygen
atoms
Nesosilicates - Isolated
Tetrahedra
Representatives:
•Garnet
•Kyanite
•Olivine
Sorosilicates - Paired Tetrahedra
Epidote is the
most common
example
Cyclosilicates - Rings
•Beryl (Emerald)
•Tourmaline
Inosilicates - Chains
Single Chains (Pyroxenes)
Inosilicates - Chains
Double Chains (Amphiboles)
Phyllosilicates - Sheets
Phyllosilicates - Sheets
Si2O5 sheets with layers of Mg(OH)2 or Al(OH)3
• Micas
• Clay minerals
• Talc
• Serpentine (asbestos) minerals
Tectosilicates - ThreeDimensional Networks
• Quartz
Feldspars
Unit Cells
All repeating patterns can be described in terms
of repeating boxes
The problem in Crystallography is to reason
from the outward shape to the unit cell
Which Shape Makes Each Stack?
Stacking Cubes
Some shapes that result from
stacking cubes
Symmetry – the rules behind the
shapes
Symmetry – the rules behind the shapes
The Crystal Classes