Minerals

What Is a Mineral?

• A mineral is a solid, naturally occurring substance that has a specific chemical composition and a highly ordered internal (crystalline) structure.

What is a Rock?

• A solid, cohesive aggregate of grains of one or more minerals

CRYSTAL - A mineral grain displaying the characteristics of its atomic structure.

- Over 4300 different kinds of minerals (most due to life!)

- differences result from the different elements used and the ways they are bonded

Chemistry Review :

An ELEMENT is determined by the number of PROTONS (+).

IONS - Atoms where the number of ELECTRONS (-) have been added or subtracted.

ISOTOPES - Atoms where the number of NEUTRONS have been added or subtracted.

The Structure of the Atom

• Atomic number= Number of protons Elements

• Atomic Mass= Number of protons + neutrons Isotopes

Periodic Table of the Elements

The Structure of the Atom

• Atomic number= Number of protons Elements

• Atomic mass= Number of protons + neutrons Isotopes

Chemical Bonds – Forces that keep atoms together

Bonds are strong when the outermost electron energy levels are complete.

# of electrons in Total # of

outermost energy level electrons

2 2

8 10

8 18

18 36

18 54

Etc.

The Structure of the Atom

• The size of atom is determined by electron cloud of the ION

Changing Model of the Atom

Changing Model of the Atom

Changing Model of the Atom

Changing Model of the Atom

Changing Model of the Atom

How Atoms Bond

Types of bonding• Ionic• Covalent• Metallic• Intermolecular

Atoms gain or lose electrons, becoming negatively charged ions or positively charged ions that attract each other.

Figure 2-7

IONIC BOND

Ex: Halite (salt)

Q: Which is Na? Cl?

How Atoms BondHow Atoms Bond

How Atoms Bond

Types of bonding• Ionic• Covalent• Metallic• Intermolecular

Sharing of electrons between similar atoms

– strongest type of bond

How Atoms Bond

Types of bonding• Ionic• Covalent• Metallic• Intermolecular

Electrons move continually among close-packed nuclei.

How Atoms Bond

Types of bonding• Ionic• Covalent• Metallic• Intermolecular

Weak attraction between molecules due to an uneven distribution of electrons – van der Waals bond.

Mineral Stability• Ion charges must sum to ZERO• Ion sizes must be compatible (electron cloud)

Mineral Stability

Mineral Stability

Mineral Stability• Temperature and pressure play defining roles in

establishing stability of mineral

Mineral Stability

• Why are there different forms of ice at different temperatures and pressures?

Mineral Stability

• Why are there different forms of ice at different temperatures and pressures?

• Because the ion sizes change, relative to each other, at different T & P, so the ideal packing changes.

Mineral Stability

• How might stishovite occur naturally?

Mineral Stability

• How might stishovite occur naturally?

• Meteorites!

Minerals are clues to the past!

Mineral Stability• How might

stishovite occur naturally?

• Meteorites!

• Why are they still at the surface?

Minerals are clues to the past!

Mineral Stability• How might

stishovite occur naturally?

• Meteorites!

• Why are they still at the surface?

• Metastability (too cold to change back)

Minerals are clues to the past!

Diamonds only form naturally more than about 150 km beneath the surface.

They are unstable at the surface – they will burn in a fire.

Mineral Composition

Rock-Forming Minerals

A. Silicates– e.g., quartz (SiO2), orthoclase (KAlSi3O8)

B. Non-silicate mineral groups– Carbonates - e.g., calcite (CaCO3), dolomite (MgCa(CO3)2)

– Oxides - e.g., hematite (Fe2O3), magnetite (Fe3O4)

– Sulfides - e.g., pyrite (FeS2), galena (PbS)

– Sulfates - e.g., gypsum (CaSO4)

– Natives - e.g., gold (Au), silver (Ag), diamond (C), platinum (Pt)

A. Silicates– e.g., quartz (SiO2), orthoclase (KAlSi3O8)

B. Non-silicate mineral groups– Carbonates - e.g., calcite (CaCO3), dolomite (MgCa(CO3)2)

– Oxides - e.g., hematite (Fe2O3), magnetite (Fe3O4)

– Sulfides - e.g., pyrite (FeS2), galena (PbS)

– Sulfates - e.g., gypsum (CaSO4)

– Natives - e.g., gold (Au), silver (Ag), diamond (C), platinum (Pt)

SilicatesMake up 90% by weight of Earth’s crust

• Si and O are the two most abundant elements in the Earth’s crust (differentiation).

• Small silicon ions fit snugly in the niches among large closely packed oxygen ions.

• Si and O are the two most abundant elements in the Earth’s crust (differentiation).

• Small silicon ions fit snugly in the niches among large closely packed oxygen ions.

Silica Tetrahedron:

Slightly changing the different elements that combine with silica greatly changes the mineral that results, or the characteristics of the mineral.

Ex/ Different forms of quartz

Types of Silicates

• Independent tetrahedra• Single chains• Double chains• Sheets• Framework

Example:Olivine

Types of Silicates

• Independent tetrahedra• Single chains• Double chains• Sheets• Framework

Example: Pyroxene

Types of Silicates

• Independent tetrahedra• Single chains• Double chains• Sheets• Framework

Example:Amphibole

Types of Silicates

• Independent tetrahedra• Single chains• Double chains• Sheets• Framework

Example:Muscovite

Types of Silicates

• Independent tetrahedra• Single chains• Double chains• Sheets• Framework

Example:Quartz

Visit the EPS Mineral Collection

Only did up to here on 9/16 (it took an hour), to leave a half-hour for more planetary stuff

Identifying Minerals

• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Crystal form• Density• Laboratory

tests

A mineral’s chemical composition and crystal structure give it a unique combination of chemical

and physical properties we can use to identify it.

Identifying Minerals

• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Crystal form• Density• Laboratory

tests

Identifying Minerals

• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Crystal form• Density• Laboratory

tests

Identifying Minerals

• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Crystal form• Density• Laboratory

tests

Identifying Minerals

• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Crystal form• Density• Laboratory

tests

Identifying Minerals

• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Crystal form• Density• Laboratory

tests

Identifying Minerals

• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Crystal form• Density• Laboratory

tests

Figure 2-20

Identifying Minerals

• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Crystal form• Density• Laboratory

tests

Identifying Minerals

• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Crystal form• Density• Laboratory

testsStibnite

Identifying Minerals

• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Crystal form• Density• Laboratory

testsFigure 20-22

Identifying Minerals

• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Crystal form• Density• Laboratory

tests EPS Electron Microprobe

Fluorescent lighting spectrum peaks

Fluorescent lighting spectrum peaks

Peak number Wavelength of peak (nm) Species producing peak1 405.4 mercury2 436.6 mercury3 487.7 terbium4 542.4 terbium 5 546.5 mercury6 577.7 terbium7 580.2 mercury or terbium 8 584.0 terbium from Tb3+ or europium in Eu+39 587.6 europium in Eu+310 593.4 europium in Eu+311 599.7 europium in Eu+312 611.6 europium in Eu+313 625.7 terbium from Tb3+14 631.1 europium in Eu+315 650.8 europium in Eu+316 662.6 europium in Eu+317 687.7 europium in Eu+318 693.7 europium in Eu+319 707 and 709 europium in Eu+320 712.3 europium in Eu+321 760.0 argon22 811.0 argon