GEOL 1330 (Hauptvogel Spring 16) LECTURE 4 & 5 - Minerals
GEOL 1330 (Hauptvogel Spring 16) LECTURE 4 & 5 - Minerals GEOL 1330
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This 6 page Class Notes was uploaded by Julian Quesada on Sunday February 14, 2016. The Class Notes belongs to GEOL 1330 at University of Houston taught by Dr. Daniel Hauptvogel in Spring 2016. Since its upload, it has received 160 views. For similar materials see Physical Geology in Geology at University of Houston.
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Date Created: 02/14/16
GEOL 1330 LECTURES 4 & 5 - MINERALS What are Minerals -5 key points to the definition -Naturally Occurring - Not artificial -Inorganic - Not living -Solid -Definite chemical composition -Specific crystal structure -Top Hat Question -Is glass a mineral? -No, glass is not a mineral, it does not have a specific crystalline structure that minerals typically take on -Is table salt a mineral? -Yes, it fits each of the five characteristics -Mineral: Natural (Iron Ore), Solid (Sand - Quartz), Inorganic (Rock Salt), Ordered Atomic Structure (Emerald) -Non-mineral: Artificial (Cast Iron), Liquid (Sea water), Gas (Air), Organic (Vegetation), Disordered Atomic Structure (Beer bottles, windows - glass) -Most rocks are Aggregates of different minerals -Ex: Granite is a rock composed of Quartz, Hornblende, and Feldspar -Minerals are composed of elements -A substance that cannot be decomposed into a simpler substance -Basic building blocks of minerals -Over 100 elements are known (92 naturally occurring) -Elements are composed of atoms -Smallest particles of matter -Protons, neutrons, electrons -Retains all the minerals' characteristics Structure of an Atom -Central region called the nucleus -Consists of protons (+ charge) and neutrons (no charge) -Make up most of the weight of an atom -Electrons (- charge) surround the nucleus -Located in energy levels called shells -Outermost shell: Valence Electrons -Model atom has no net charge -# of protons = # of electrons -Ions - charged atoms due to loss or gain of an electron -Cations = +charged atoms -Anions = -charged atoms -Octet Rule - atoms gain, lose, or share electrons in order to obtain stable electron configuration of the noble gasses (8 valence electrons) Bonding -Chemical Bonding -A strong attractive force that links atoms together -Compound - 2 or more elements bonded together -Ionic Bonding - atoms gain or lose outermost (valence) electrons to form ions -Ionic compounds consist of an orderly arrangement of oppositely charged ions -Covalent Bonding - Atoms share electrons -Generally stronger than ionic bonds -Both ionic and covalent bonds can occur in the same compound -Top Hat Question -What type of bonds hold together the water molecule -Covalent Formation and Structure of Minerals -Minerals form in 3 primary ways -Crystallization from cooling magma/lava -Most common -Types of Minerals that form are dependent on temperature and chemistry of the magma -Precipitation out of a solution -Water that is saturated in a substance will precipitate these ions in a solid form (ex: salt) -Biologic processes -Usually accumulation of fossils -Minerals consist of an orderly array of atoms (crystalline structure) -Chemically bonded to form a particular crystalline structure -Crystalline structure in ionic compounds determined by -Ion size -Charge of ions -Polymorphs - minerals with the same composition but different crystalline structure -Ex: Diamonds and graphite are both made of carbon Physical Properties of Minerals -Several physical properties are used to identify minerals -Involves simple tests or observations -Common physical properties include: -Color -Luster -Streak -Hardness -Breakage -Crystal Habit -Color -Generally not diagnostic property for mineral identification -Often high variable due to slight changes in mineral chemistry -Exotic colorations of certain minerals produce gemstones -Luster -Appearance of a mineral in reflected light -Metallic -Nonmetallic -Other descriptive terms exist -Streak -Color of a mineral in powdered form -Generally only good for identifying metallic minerals -Hardness -Resistance of a mineral to abrasion or scratching -Moh's scale of hardness -Breakage -Cleavage -Tendency to break along planes of weak bonding -Produces flat, shiny surfaces -Described by resulting geometric shapes -Number of planes -Angles between adjacent planes -Fracture -Uneven or curved breakage across strong bonds -Common Cleavages (Not tested over) -Cleavage Direction 1 - Shape = Flat Sheets -Cleavage Direction 2 @ 90* - Shape = Elongated form w/ rectangle cross section -Cleavage Direction 2 not @ 90* - Shape = Elongated form with parallelogram cross section -Cleavage Direction 3 @ 90* - Shape = Cube -Cleavage Direction 3 not @ 90* - Shape = Rhombohedron -Cleavage Direction 4 - Shape = Octahedron -Fracture: Minerals do not break along bonds of weakness -Very irregular, often curvy (conchoidal) -Other Properties -Density -Magnetism -Reaction to acid -Malleability -Double refraction -Taste -Smell -Elasticity Elements in the Earth's Crust -Top Hat Question -Which two elements are the most abundant in the Earth's crust -Answer: Oxygen and Silicon -Distribution of the elements in the Earth's crust -Oxygen -Silicon -Iron -Potassium -Magnesium -Sodium -Calcium -Aluminum -Other Common Mineral Groups -Examples: -Silicates: (SiO4)^-4 e.g. Quartz -Carbonates: (CO3)^-2 e.g. Calcite -Halides: (Cl)^-2 e.g. Halite -Oxides: O^-2 e.g. Magnetite -Sulfers: S^-2 e.g. Pyrite -Sulfates -Native Elements -Silicate minerals are very abundant due to large % of silicon and oxygen in the crust Silicon-Oxygen Tetrahedron -The fundamental building block of the silicate group -One silicon atom bonded with 4 oxygen atoms (SiO4)^4- -Each O^2- atom gets 1 electron from Si^4+, leaving each oxygen with a -1 charge -Because the charge is overall negative, tetrahedra bond with positive ions to form a stable compound -Usually with Fe, Mg, K, Na, Al, and Ca -Isolated Silicate Tetrahedra: Olivine -Tetrahedra can link together to form chains and sheets -Framework Silicates: Shape is in random direction, chaotic -Quartz -Feldspar -Top Hat Question -How many planes of cleavage will a single chain silicate form? -2 planes at 90 degrees -All single chains have 2 cleavages at 90 degrees and double chains have 2 cleavages at 65 degrees -Common substitutions AL and Si, Fe and Mg, Na, Ca, and K Rock-Forming Silicates -rock forming silicates -Olivine -Pyroxene -Amphibole -Biotite -Muscovite -Orthoclase (Potassium Feldspar) -Plagioclase -Quartz -Mafic -Olivine -Pyroxene -Amphibole -Biotite -Felsic -Muscovite -Orthoclase -Plagioclase -Quartz
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