2 - MINERALS Building Blocks of Rocks

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2 - MINERALSBuilding Blocks of Rocks

• Matter Atomic Structure
• Bonding
• Minerals
• Physical properties of minerals
• Major rock-forming mineral families
• Silicates - rock-forming SUPER STARS

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Structure of an Atom
Protons /1 Neutrons 0/1 Electrons -/0
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Two-dimensional representation of a 12C atom
Fig. 3.1B
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BONDING - 4 kinds

• IONIC - electrical charge
• COVALENT - sharing
• METALLIC - inner shell covalent bond
• INTERMOLECULAR - Van der Waals

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IONIC BONDING - electrical
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Covalent Bonding in Diamond
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Covalent Bonds in Water
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Carbon Atoms in Graphite
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MINERALS - Rock Builders

• NATURALLY FORMED
• INORGANIC
• CRYSTALLINE SOLID
• DIAGNOSTIC CHEMICAL COMPOSITION

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Galena (PbS)
CRYSTALLINE SOLID
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Atomic Structure of Galena
Sulfur
Lead
DIAGNOSTIC CHEMICAL COMPOSITION
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Ionic Radii charge of some geologically
important ions allows ionicsubstitution or
SOLID SOLUTION
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WHAT FACTORS DETERMINE WHAT MINERAL WILL FORM?

• WHAT ELEMENTS ARE AVAILABLE
• ABUNDANCE OF EACH ELEMENT
• SIZE CHARGE OF EACH ELEMENT
• ENVIRONMENT - SPACE, PRESSURE, TEMPERATURE

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Irregular Intergrowth of Quartz
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BandedAgate
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Identify Minerals by Their Physical Properties

• Crystal Habit
• Cleavage Fracture
• Striations
• Hardness

• Specific Gravity
• Color
• Streak
• Luster
• Acid Test

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Constancy of Interfacial and Angles in Quartz
Crystal Form - Constancy of Interfacial Angles
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Cleavage
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StriationsPyrite (Fools Gold)FeS)
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Examples
MOHS HARDNESS SCALE
Brian Skinner
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The Different Colors of Corundum
Ruby
Sapphire
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Streak - color of rock power
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GALENA (Pb S) - Identified by crystal habit
luster specific gravity hardness
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Acid Test
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Average Composition of the Continental Crust
O
O
Si
Weight Percent
Volume Percent
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COMMON ROCK-FORMINGMINERAL FAMILIES

• NATIVE ELEMENTS - GOLD, COPPER
• HALIDES - PRECIPITATES
• OXIDES - 1 METAL OXYGEN
• SULFIDES - 1 METAL SULFUR
• SULFATES - (SO4)2-
• CARBONATES - (CO3)2-
• SILICATES - SUPER STARS!!!

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One view of the Silica Tetrahedron
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More Views of the Silica Tetrahedron
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Linking Silicate Tetrahedra
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About Silicates

• There are 2 families of silicates
• FERROMAGNESIAN SILICATES - Fe/Mg -gt MAFIC
  MINERALS
• NONFERROMAGNESIAN or ALUMINO- SILICATES -gt FELSIC
  MINERALS

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Olivine
(Mg,Fe)2SiO4
formed from single silica tetrahedra
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Cleavage in the Chain Silicates
Pyroxene
Amphibole
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Framework (example quartz)
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Clay a sheet silicate
SHEET SILICATES
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GREEN FELDSPAR
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Polished Section
1 cm
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Thin Section
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Thin section under ordinary light
Magnetite
Feldspar
Mica
Quartz
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Thin section under polarized light