Exam 1: Mineralogy

Information from Lecture 1 to Exam 1: Mineralogy

Order of the creation of Earth.

1. Big Bang

2. Solar Nebula’s collapse to form protoplanetary disks

3. Accretion of planetismals

4. Formed from “Potato” to Spherical

5. Magma Earth

6. Mars sized impactor takes a bite out of earth to form the moon (maybe gave us h2o)

What is Accretion of Planetesimals?

Addition of material to a photo-planet.

What is Earth trying to do with it’s heat?

Release its heat

How did the layers of the Earth form?

Heavy elements sunk to the center (iron, nickel) and lighter metals rose to the surface

What is the radius of the Earth?

6371 km

The core is composed of what?

Solid inner core, Liquid Outer core

The liquid core controls what?

The Earth’s magnetic field

The mantle is composed of what?

Upper Mantle, Lower Mantle, Asthenosphere

The Asthenosphere contains what volume percentage of what?

10% melt

T/F: The asthenosphere is strong and solid

False, the asthenosphere is weak and liquid

We know the layers of the Earth because of what?

S-Waves and P-Waves

Lithosphere contains what?

Crust and Upper Mantle

Upper Mantle releases heat through what method?

Conduction

The lithosphere is what and what?

Strong and Cold

Two types of crust

Oceanic and Continental

Oceanic Crust is what and what?

Dense and thin (7km)

Continental crust is what and what?

Less dense, thicker (~35km)

The oceanic crust is composed of what?

Mafic rocks like Basalt and Gabbro

What elements are found in Oceanic crust?

iron, calcium, and magnesium

What is continental crust composed of?

felsic rocks like granites

What elements are found in continental crust?

Silicon, aluminium

Mafic rocks are

Igneous rocks rich in magnesium and iron. Typically dark and composed of olivine and pyroxene

Felsic rocks are

Igneous rocks rich in silica. Typically light colored and composed of feldspar and quartz.

Average heat gradient as you go into the Earth.

25 Celcius per km

What are the 3 Driving Factors of Heat in the Earth?

1. Heat of Collision

2. Crystallization of the outer core

3. Radioactive Decay

What is radioactively decaying in Earth?

Uranium, Thorium, Potassium

Where does Earth lose its most energy?

The Ocean

Where are you most likely to find conduction on Earth?

Lithosphere

Where are you most likely to find convection in the Earth?

Mantle

Where are you most likely to find radiation?

The sun

Plate Tectonics is the theory of what?

A 1960s theory that claims the rigid lithospheric plates move in response to the convecting mantle.

Who proposed evidence of Seafloor spreading?

Henry Hess

What is the Vine-Matthews Hypothesis?

The motion of oceanic plates on either side of an oceanic ridge

What are the 5 types of Plate Boundaries?

1. Divergent Oceanic

2. Divergent Continental

3. Convergent Oceanic and Continental

4. Transform Continental

5. Mantle Plume and Triple Junction

What is a rock?

A mixture of minerals

Monomineralic

A rock composed of a single mineral

Polymineralic

A rock composed of many minerals

Definition of a mineral

1. Crystalline Structure

2. Homogenous Solid

3. Definite Chemical Composition

4. Inorganic

5. Occurs Naturally

Are glasses considered minerals?

No! They are amorphous and lack ordered atomic structure

What is a Trace Element?

Small amounts of impurities in chemical composition that do not require you to note them in the molecular formula.

How can you tell a real from a lab grown mineral?

Moh’s Hardness Scale and Density

What is an ionic bond?

Electrons swapped

What is a covalent bond?

Electrons shared

What is a metallic bonds?

Sharing of free electrons among a lattice of cations

What are Van Der Waal bonds?

London Bonds/Hydrogen Bonds

What is Isotropic?

Same in all directions

What is Anisotropic?

Varies with direction

What is the Coordination Number?

The number of anions that surround a central cation.

What are Pauling’s Rules?

1. Coordination Principle

2. Electrostatic Valency Principle

3. Sharing of Polyhedral Elements I

4. Sharing of Polyhedral Elements II

5. Principle of Parsimony

What is the Coordination Principle?

• Anions surrounding a cation form a coordination polyhedron

• Distance between a cation and antion is equal to the sum of their radii

• Shape of the polyhedron is determed by the cation to anion radius ratio

What is the Electrostatic Valency Principle

• The sum of the strength of valence bonds reacing a cation from all neighboring anions is equal to the charge of the cation

• ev = | charge on cation / CN |

What is sharing of Polyhedral Elements I?

Sharing edges or faces by neighboring coordination polyhedra decreases the stability of a crystal structure

What is sharing of polyhedral elements II?

Cations with high valence and small radii tend not to share edges, they share apices

What is the Principle of Parsimony?

Mineral lattice that contains small number of sites can accommodate large numbers of elements will have extensive substitution.

A coordination number of 2 means the configuration is what and the radius ratio is what?

Linear, less than 0.155

A coordination number of 3 means the configuration is what and the radius ratio is what?

Trigonal, between 0.155 and 0.225

A coordination number of 4 means the configuration is what and the radius ratio is what?

Tetrahedral, between 0.225 and 0.414

A coordination number of 6 means the configuration is what and the radius ratio is what?

Octahedral, between 0.414 and 0.732

A coordination number of 8 means the configuration is what and the radius ratio is what?

Cubic, between 0.732 and 1.000

When can one cation substitute for another?

When their radii are within ~15% of each other and the formulas stay electrostatically neutral

All factors that affect the degree of substitution

1. Radius Size

2. Valence Charge

3. Temperature of Substitution

4. Availability of Atoms

What is cation exchange?

One cation leaves, another enters

The motion of cations is driven by what processes?

Kinetic processes

What is simple substitution?

One for one sub. of cations

What is coupled substitution?

Exchanging ions have different charges, so they grab a buddy to sub w/ them

What minerals are in the core?

Iron and Nickel

How many crystal classes are there?

32

What type of crustals reveal symmetry?

Euhedral or Fully formed

What is a motif?

A geometric feature that expresses symmetry of an ordered arrangement.

How to calculate rotation?

360/n

What is reflection?

Occurs across a plane (mirrored)

What is inversion

Occurs through a point

What is rotoinversion?

A combination of rotation and inversion

2-fold rotoinversion means what?

You rotate the motif by n and then invert through the center of symmetry.

What is the letter for inversion?

i

What is the letter for mirror?

m

Crystal classes can be described by combining what and what?

The five rotation axes and the five rotoinversion axes

What is a unit cell?

A subset of points that can be repeated to fully represent the symmetry of a structure

What is crystal morphology determined by

The shape and summetry of the unit cell if the mineral is FULLY formed

What are the seven crystal systems?

Triclinic, Monoclinic, Orthorhombic, Tetragonal, Isometric, Trigonal, Hexagonal

What are the characteristics of a Triclinic System

1. a ≠ b ≠ c

2. No angles = 90^o

What are the characteristics of a Monoclinic System

1. a ≠ b ≠ c

2. Two angles 90^o

3. Beta Angle > 90^o

What are the characteristics of an orthorhombic system?

1. b > a > c

2. Two angles = 90^o

3. Only has 2-fold axes and 2 mirror planes

What are the characteristics of a tetragonal system?

1. a = b ≠ c

2. All angles are 90^o

3. Either single 4-fold or 4-fold rotoinversion

What are the characteristics of an isometric (cubic) system

1. a = b = c

2. All angles 90^o

3. Either 4 3-fold axes or 4 3-fold rotoinversion axes

What are the characteristics of a trigonal system?

1. 3 axes

2. a = b= c

3. All angles equal but never are 90^o

What are the characteristics of a hexagonal system?

1. Four axes

2. a = b = d ≠ c

3. Atleast 1 6-fold or 3-fold axis

4. 120 degree separation in horizontal plane perpendicular to c

What is the general chemical composition of Quartz?

SiO₂

What is the general chemical composition of Olivine?

(Mg, Fe)₂SiO₄

What is the general chemical composition of Pyroxenes?

(smith)₂Si₂O₆

What is the general chemical composition of Orthopyroxenes?

(Fe, Mg)₂Si₂O₆

What is the general chemical composition of Clingopyroxenes?

CaMgSi₂O_{6 (can contain Fe or Mg)}

What is the general chemical composition of Plagioclase?

NaAlSi₃O₈

CaAl₂Si₂O₈

What is the general chemical composition of K-Felspars?

KAlSi₃O₈

Where do you find Quartz in the Earth?

Continental crust

Where do you find olivine in the Earth?

Basalt (oceanic crust)

Orthopyroxenes are high in what?

Iron and Magnesium

Clinopyroxenes are high in what?

Calcium + Fe or Mg

What is a polymorph?

Same chemical formula but multiple structures (quartz)

How can you find (hkL)?

(h/d k/d L/d)