MNE 210 Exam 1 Comprehensive Study Notes

Exam Logistics and Reminders

• Exam 1 Schedule: The exam will take place on Tuesday, February 10th, in room Mines 225.
• Exam Format: The assessment includes a combination of pencil and paper questions as well as practical mineral identification.     * Question Types: True/False, Multiple choice, Free Response, and Fill in the blank.     * Mineral Identification: Students must be able to identify minerals covered in Labs 1 through 3.
• Immediate Schedule Items:     * A quiz will be administered today following the review session.     * There are no labs scheduled for the upcoming week.     * A guest speaker is scheduled for next Thursday. A subsequent quiz will cover the material presented by the speaker.

Definition of a Mineral

• Criteria for a Mineral: To be classified as a mineral, a substance must satisfy five specific criteria:     * Naturally occurring: It must be formed by natural geological processes, not synthesized by humans.     * Atomicly arranged: It possesses an ordered internal crystalline structure.     * Solid: It must be a solid at stable Earth surface conditions.     * Inorganic: It is generally not produced by biological processes.     * Definite homogeneous chemical composition: It can be expressed by a specific chemical formula.         * Example: Salt (Halite) is defined by the chemical formula $NaCl$.

Composition of the Earth's Crust

• Dominant Mineral Classes: The crust is primarily composed of the following mineral groups:     * Silicates     * Oxides     * Carbonates     * Sulfates
• Elemental Abundance: The majority of the Earth's crust is comprised of eight specific elements:     1. Oxygen ($O$)     2. Silicon ($Si$)     3. Aluminum ($Al$)     4. Iron ($Fe$)     5. Calcium ($Ca$)     6. Sodium ($Na$)     7. Potassium ($K$)     8. Magnesium ($Mg$)

Mineral Classification and Silicate Subtypes

• Major Mineral Classes:     * Halides: Elements combined with Halogens.     * Oxides: Elements combined with Oxygen ($O$).     * Sulfides: Contain the sulfide ion ($S^{2-}$).     * Phosphates: Contain the phosphate group ($PO_4^{3-}$).     * Carbonates: Contain the carbonate group ($CO_3^{2-}$).     * Sulfates: Contain the sulfate group ($SO_4^{2-}$).     * Silicates: Contain Silicon and Oxygen ($Si-O$).
• Types of Silicates (Categorized by Structure):     * Nesosilicates ($SiO_4$): Isolated tetrahedra. Examples include Olivine and Garnet.     * Sorosilicates ($Si_2O_7$): Paired tetrahedra. Examples include the Epidote group.     * Cyclosilicates ($Si_3O_9$): Ring structures. Examples include Beryl and Tourmaline.     * Inosilicates: Chain structures.         * Single Chain: Pyroxenes.         * Double Chain: Amphiboles.     * Phyllosilicates ($Si_4O_{10}$): Sheet structures. Examples include Micas and Clays.     * Tectosilicates ($SiO_2$): Framework structures. Examples include Quartz and Feldspars.

Principles of Mineral Identification

• Mohs Scale of Hardness: Mnemonics for remembering the 10 minerals of the Mohs scale:     * "To Get Candy From Aunt Fanny Quit Teasing Cousin Danny"     * "Tall Goats Chew Fresh Apples On Quiet Tall Cliffs Daily"     * "Tiny Green Cats Fly Across Old Quiet Towns Carefully Dancing"
• Cleavage vs. Fracture:     * Cleavage: The tendency of a mineral to break along definite, smooth planes. This is dependent on the crystal structure and always results in smooth breaks. Examples include Basal, Pinacoidal, Rhombohedral, and Prismatic cleavage.     * Fracture: The way a mineral breaks when it lacks crystallographic control. These breaks are NOT smooth. Examples include Conchoidal, Hackly, Irregular, and Splintery fractures.
• Luster: Describes the way a mineral reflects light from its surface.     * Non-Metallic: Includes Adamantine, Vitreous, Resinous, Earthy, and Silky.     * Metallic: Includes Metallic and Submetallic.
• Transparency: An optical property based on the percentage of light that can penetrate the mineral.     * Opaque: Light does not penetrate; the mineral is not see-through at all.     * Translucent: Light passes through, but you cannot read text through the mineral.     * Transparent: Light passes through clearly; you can see and read through the mineral.
• Color: Color is NOT a reliable identifying factor and should never be used as the sole method for identification.
• Streak: The color of a mineral in its powdered form, which remains unchanging regardless of the mineral's external color.     * White streak plate: Has a hardness of approximately $6$. Quartz will not show a streak on this plate.     * Black streak plate: Has a hardness of approximately $7.5$. Quartz will show a streak on this plate.
• Habit: The external shape or form in which a mineral tends to grow or form natively. Habit is distinct from the crystal system.     * Tabular: Plate-like.     * Acicular: Needle-like.     * Fibrous: Fiber-like.     * Massive: No distinguishing crystal form is visible.
• Crystal Systems: Refers to the internal atomic arrangement. There are 6 systems:     1. Cubic     2. Orthorhombic     3. Tetragonal     4. Hexagonal     5. Monoclinic     6. Triclinic

Bowen’s Reaction Series and Mineral Association

• Mineral Association: Specific minerals are often found together due to shared conditions of formation, including:     * Temperature of formation     * Chemical compatibility     * Geologic environment     * Mineral class     * Practical Application: If one mineral is identified, its neighbors can often be predicted or narrowed down based on these associations.
• Bowen’s Reaction Series Components:     * Continuous Series (Plagioclase Feldspars): The transition from Calcium-rich to Sodium-rich minerals. The sequence is: Ca-Anorthite $\rightarrow$ Bytownite $\rightarrow$ Labradorite $\rightarrow$ Andesine $\rightarrow$ Oligoclase $\rightarrow$ Na-Albite.     * Discontinuous Series (Ferromagnesian/Mafic Silicates): The sequence of formation as temperature drops: Olivine $\rightarrow$ Orthopyroxene $\rightarrow$ Clinopyroxene $\rightarrow$ Amphibole $\rightarrow$ Biotite.
• Crystallization Drivers:     * High Temperature ($1200^{\circ}C$): Mafic minerals (high in $Fe$, $Mg$, and $Ca$) crystallize first. Includes Olivine and Calcium-rich Plagioclase.     * Low Temperature ($600^{\circ}C$): Felsic minerals (high in Silica, $Na$, $Al$, and $K$) crystallize last. Includes Quartz, Muscovite (White Mica), and Orthoclase (K-feldspar).     * Residual Phases: The last components to crystallize include K-Spar, Muscovite, and finally Quartz.
• Petrology and Temperature Correlations:     * $1500^{\circ}C$: Dunite Rocks (Olivine, Chromite).     * $1300^{\circ}C$: Norite Rocks (Anorthite, Bytownite, Orthopyroxene).     * $1100^{\circ}C$: Gabbro (Labradorite, Magnetite).     * $900^{\circ}C$: Diorite/Granitoid Rocks (Andesine, Clinopyroxene/Augite, Magnetite).     * $800^{\circ}C$: Monzonite Rocks (Oligoclase, Hornblende).     * $600^{\circ}C$: Granite (K Feldspar, Albite, Na, Biotite).     * $300-600^{\circ}C$: Pegmatite (Quartz, Muscovite).     * Low Temperature: Hypogene Hydrothermal solutions.

Pauling’s Rules

• Overview: Published by Linus Pauling in 1929 to predict and rationalize the crystal structures of ionic compounds.
• Rule 1: The Coordination Principal: A coordination polyhedron of anions forms around each cation. The distance between the cation and anion equals the sum of their packing radii. The radius ratio ($R_x/R_z$) of the cation to the anion determines the coordination number and the shape of the polyhedron.
• Rule 2: The Electrostatic Valency Principle: An ionic structure is stable if the sum of the strengths ($S$) of the electrostatic bonds reaching an anion from adjacent cations equals the charge ($Z$) on that anion.
• Rule 3: Sharing of Polyhedral Elements I: Sharing edges or faces between two anion polyhedra decreases stability. More shared corners result in closer cations, leading to destabilizing cation-cation repulsion.
• Rule 4: Sharing of Polyhedral Elements II: In structures with different cations, those with high valency and small coordination numbers tend not to share polyhedral elements with one another.
• Rule 5: The Principle of Parsimony: The number of different kinds of constituents in a crystal tends to be small. For example, Amphiboles have few distinct crystallographic sites despite a wide range of chemical constituents.
• Prewitt’s Addendum: Ensuring the chemical formula is charge-balanced, the sum of the coordination numbers of all cations must equal the sum of the coordination numbers of all anions. This helps choose between possible coordination numbers for an anion by ensuring the number of bonds to cations equals the number of bonds to anions.

Study Recommendations

• Lab Review: Re-examine samples in the rock room downstairs.
• Quiz Review: Look over past quizzes. Graded quizzes from today can be picked up during lab or from Ed tomorrow.
• Material Gaps: The review slideshow is not exhaustive. Candidates should independently study:     * Twin Types     * Atomic bonding types (Covalent, Ionic, Metallic, etc.)     * Isostructuralism     * Polymorphs     * Specific Silicate structures