MINERALS Introduction What Are They? Physical Properties & Identification Atoms & Elements Mineral Groups.

MINERALS

• Introduction• What Are They?• Physical Properties & Identification• Atoms & Elements• Mineral Groups

Minerals

Introduction

GEOL 131: Minerals - Intro

Eight Most Abundant Elements in Earth’s Crust

GEOL 131: Minerals - Intro

Some of the Most Abundant Minerals in Earth’s Crust

• Quartz

• Feldspars

• Micas

GEOL 131: Minerals - Intro

Some of the Most Abundant Minerals in Earth’s Crust

• Amphiboles

• Pyroxenes

• Olivine

GEOL 131: Minerals - Intro

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MineralsMinerals

What Are They?

Minerals Are:

• Solid

• Naturally occurring

• Inorganic

GEOL 131: Minerals – What Are They?

Minerals Have:

• Well-defined chemical compositions

• Well-ordered atomic structures

GEOL 131: Minerals – What Are They?

Minerals

Physical Properties & Identification

Physical Properties

• Each mineral has a unique set of properties

• Determined by mineral’s chemical composition and atomic structure

• Properties are used to identify unknown minerals

GEOL 131: Minerals – Physical Properties & Identification

Physical Properties Commonly Used in Identification

• Color• Streak• Luster• Cleavage • Crystal habit• Striations• Hardness• Effervescence• Magnetism

GEOL 131: Minerals – Physical Properties & Identification

COLOR

GEOL 131: Minerals – Physical Properties & Identification

Quartz

• Easy to observe, but can be misleading• Impurities can produce different colors

STREAK• Color of powdered mineral• More reliable than “bulk” color

GEOL 131: Minerals – Physical Properties & Identification

Streak plate

LUSTER• How sample reflects light• Not the same as color

GEOL 131: Minerals – Physical Properties & Identification

METALLIC luster NONMETALLIC luster

LUSTER• How sample reflects light• Not the same as color

GEOL 131: Minerals – Physical Properties & Identification

Both of these minerals have a METALLIC luster

CLEAVAGE

• How sample cleaves (breaks)

• Always the same for a given mineral

• Three aspects– Quality– Number of directions– Angle

GEOL 131: Minerals – Physical Properties & Identification

CLEAVAGE QUALITY - None

GEOL 131: Minerals – Physical Properties & Identification

No cleavage: irregular breakage surface

CLEAVAGE QUALITY - GoodGEOL 131: Minerals – Physical Properties & Identification

Good cleavage: somewhat regular breakage surface

Note “stair-step” pattern

CLEAVAGE QUALITY – Excellent/perfectGEOL 131: Minerals – Physical Properties & Identification

Excellent cleavage: smooth breakage surface

# OF CLEAVAGE DIRECTIONS

GEOL 131: Minerals – Physical Properties & Identification

• A number

• Only applies to good or excellent cleavage quality

# OF CLEAVAGE DIRECTIONS - OneGEOL 131: Minerals – Physical Properties & Identification

One smooth surface

# OF CLEAVAGE DIRECTIONS - TwoGEOL 131: Minerals – Physical Properties & Identification

Two non-parallel smooth surfaces

# OF CLEAVAGE DIRECTIONS - ThreeGEOL 131: Minerals – Physical Properties & Identification

Three non-parallel smooth surfaces

# OF CLEAVAGE DIRECTIONS - Four

GEOL 131: Minerals – Physical Properties & Identification

Four non-parallel smooth surfaces

Fluorite

CLEAVAGE ANGLE• Angle between cleavage surfaces

GEOL 131: Minerals – Physical Properties & Identification

90-degree angle 60-degree angle

120-degree angle

CRYSTAL HABIT

GEOL 131: Minerals – Physical Properties & Identification

• How a mineral grows

• Unusual to see well-formed crystals in nature– Need space to grow

CRYSTAL HABITGEOL 131: Minerals – Physical Properties & Identification

Well-formed crystal faces

Poorly-formed crystals: not enough space

CRYSTAL HABIT• Don’t confuse a crystal face with an excellent

cleavage surface

• Crystal face – caused by growth

• Cleavage surface – caused by breaking

GEOL 131: Minerals – Physical Properties & Identification

STRIATIONS• Thin grooves on mineral’s surface

• Can be hard to see

GEOL 131: Minerals – Physical Properties & Identification

From www4.uwm.eduFrom facweb.bhc.edu

HARDNESS

GEOL 131: Minerals – Physical Properties & Identification

EFFERVESCENCEGEOL 131: Minerals – Physical Properties & Identification

Dilute hydrochloric acid (HCl)

If CO3 ion present,

carbon dioxide bubbles will form:

CaCO3(calcite) + 2HCl =

H2O + CO2 + CaCl2

MAGNETISM• Some iron-rich minerals are magnetic

GEOL 131: Minerals – Physical Properties & Identification

Magnetite (Fe3O4) attracting a magnet

MINERAL IDENTIFICATION

• Table or flowchart

• Observation of unique properties

• Narrow down possibilities

GEOL 131: Minerals – Physical Properties & Identification

MINERAL IDENTIFICATION

GEOL 131: Minerals – Physical Properties & Identification

Minerals

Atoms & Elements

All Minerals Are Made of AtomsGEOL 131: Minerals – Atoms and Elements

GEOL 131: Minerals – Atoms and Elements The Periodic Table of the Elements

http://www.ptable.com/

Basic Structure of an AtomGEOL 131: Minerals – Atoms and Elements

Valence Shells

GEOL 131: Minerals – Atoms and Elements

Atomic Bonds

• Hold atoms together to make mineral crystals

• Formed by electron interaction

• Require filled valence shells

GEOL 131: Minerals – Atoms and Elements

Atomic Bonds

GEOL 131: Minerals – Atoms and Elements

Atomic BondsGEOL 131: Minerals – Atoms and Elements

Chemical Composition of Minerals

• Elements present and in what amounts

• Well-defined: Limited or no variation

• Described by mineral’s formula

• Halite (salt): NaCl

GEOL 131: Minerals – Atoms and Elements

Atomic Structure of Minerals

• Arrangement of atoms • Well-ordered: Repeats in a regular pattern

GEOL 131: Minerals – Atoms and Elements

Atomic Structure of Minerals

• Arrangement of atoms

GEOL 131: Minerals – Atoms and Elements

QUARTZ

Atomic Structure – Diamond vs GraphiteGEOL 131: Minerals – Atoms and Elements

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS

• Silicates (largest group)• Carbonates• Sulfates• Sulfides• Oxides• Halides• Native elements

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS - Silicates• Largest group

– 90% of Earth’s crust

• Si and O atoms in a tetrahedron (pyramid)

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS - Silicates• Oxygen atoms can bond to adjacent

tetrahedra in a mineral’s atomic structure

• Forms the “backbone” of the mineral

• Example: single-chain structure– Each tetrahedron shares two oxygens with

adjacent tetrahedra

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS - SilicatesSilicate structures

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS - Silicates

• A silicate mineral’s properties depend partly on its silicate structure

– Hardness: 3-D networks make harder minerals (quartz)

– Cleavage: sheet structures produce sheet cleavage (micas)

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS - Silicates

• Example: Hardness– 3-D frameworks make harder minerals

Quartz

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS - Silicates

• Example: Cleavage– Sheet structures produce sheet cleavage

Micas

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS - Silicates

• Dark vs. light silicates

– Dark: rich in Fe and Mg

– Light: little Fe or Mg

• Important for igneous rocks (next chapter)

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS - Silicates

• Some common silicate minerals– Quartz: SiO2

– Orthoclase feldspar (aka potassium feldspar or K-spar): KAlSi3O8

– Muscovite mica: KAl2(AlSi3O10)(F,OH)2

– Hornblende: Ca2(Mg, Fe, Al)5 (Al, Si)8O22(OH)2

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS – Carbonates• CO3 ion• Effervescence• Common examples

– Calcite: CaCO3

– Dolomite: CaMg(CO3)2

– Malachite: Cu2CO3(OH)2

Malachite

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS – Sulfates

• SO4 ion• Common examples

– Gypsum: CaMgSO4*2H2O

– Anhydrite: CaMgSO4

– Barite: BaSO4

Giant gypsum crystals, Naica Mine, Mexico

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS – Sulfides

• S, no oxygen• Important metal ores• Common examples

– Galena: PbS– Pyrite: FeS– Chalcopyrite: CuFeS2

Cubic galena crystals

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS – Oxides

• Oxygen• No Si, C, or S• Common examples

– Hematite: Fe2O3

– Magnetite: Fe3O4

– Corundum: Al2O3

Red corundum (ruby)

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS – Halides

• Cl, F, or Br• Common examples

– Halite (salt): NaCl– Fluorite: CaF2

Wieliczka salt mine, Poland

GEOL 131: Minerals – Mineral Groups

MINERAL GROUPS – Native elements

• Any element in pure form• Common examples

– Sulfur (S)– Graphite (C)– Copper (Cu)

End of Minerals chapter