2 - MINERALSBuilding Blocks of Rocks
• Matter & Atomic Structure
• Bonding
• Minerals– Physical properties of minerals– Major rock-forming mineral families– Silicates - rock-forming SUPER STARS
Structure of an Atom
Protons +/1Neutrons 0/1Electrons -/0
Two-dimensional representation of a
12C atom
BONDING - 4 kinds
IONIC - electrical charge
COVALENT - sharing
METALLIC - inner shell covalent bond
INTERMOLECULAR - Van der Waal’s
IONIC BONDING - electrical
Covalent Bonding in Diamond
Covalent Bonds in Water
Carbon Atoms in Graphite
MINERALS - Rock Builders
NATURALLY FORMED
INORGANIC
CRYSTALLINE & SOLID
DIAGNOSTIC CHEMICAL COMPOSITION
Galena (PbS)CRYSTALLINE SOLID
Atomic Structure of GalenaSulfur
Lead
DIAGNOSTIC CHEMICAL COMPOSITION
Ionic Radii & charge of some
geologically important ions allows “ionic
substitution” or SOLID
SOLUTION
WHAT FACTORS DETERMINE WHAT
MINERAL WILL FORM?
WHAT ELEMENTS ARE AVAILABLE ABUNDANCE OF EACH ELEMENT SIZE & CHARGE OF EACH
ELEMENT ENVIRONMENT - SPACE,
PRESSURE, TEMPERATURE
Irregular Intergrowth of
Quartz
Identify Minerals by Their Physical Properties
Crystal Habit Cleavage &
Fracture * Striations Hardness
Specific Gravity Color Streak Luster Acid Test
Constancy of Interfacial and Angles in Quartz
Crystal Form - Constancy of Interfacial Angles
Striations:Pyrite
(Fool’s Gold)FeS)
Brian Skinner
ExamplesMOH’S HARDNESS SCALE
The Different Colors of
Corundum
Ruby
Sapphire
Streak - color of rock power
GALENA (Pb S) - Identified by: crystal habit luster specific gravity hardness
Average Composition of the Continental Crust
Weight Percent Volume Percent
SiO
O
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!!!
One view of the Silica Tetrahedron
More Views of the Silica Tetrahedron
Linking Silicate Tetrahedra
About Silicates
There are 2 families of silicates:
FERROMAGNESIAN SILICATES - Fe/Mg -> MAFIC MINERALS
NONFERROMAGNESIAN or ALUMINO- SILICATES -> FELSIC MINERALS
Olivine:
formed from single silica tetrahedra
(Mg,Fe)2SiO4
Cleavage in the Chain
Silicates
Pyroxene
Amphibole
Framework (example: quartz)
SHEET SILICATES
Clay: a sheet silicate
Polished Section
~1 cm
Thin section under ordinary light
Magnetite
Mica
Quartz
Feldspar
Thin section under polarized light