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

BandedAgate

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

Cleavage

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

Acid Test

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

GREEN FELDSPAR

Polished Section

~1 cm

Thin Section

Thin section under ordinary light

Magnetite

Mica

Quartz

Feldspar

Thin section under polarized light