ESS221 Compressed Notes.doc

17 Pages
Unlock Document

University of Toronto St. George
Earth Sciences
Grant Henderson

ESS221 Study Notes Condensed Lecture1&2:MineralProperties Mineral Definition: -Naturally occurring -Made Inorganically (mostly) -definite but not fixed chemical composition -solid crystalline structure -homogenous substance *defracts X-rays Naming Minerals Family > Group > Species > Series > Polymorphs > Varieties Family: group related by composition. eg. Tectosilicates Group: related by similar atomic structure. eg. Quartz group Species: type of group eg. alpha or beta quartz Series: same structure, different composition eg. Olivine: forsterite Mg2SiO4 and fayalite Fe2SiO4 Polymorph: different structure, same formula eg. stishovite, coesite Variety: same mineral, with distinct physical properties eg. amethyst, rose quartz Silicate Minerals: SiO4 4- Si2O7 6- Si6O18 12- Si2O6 4- Si4O11 6- Si2O5 2- SiO2 ESS221 Study Notes Condensed Diagnostic Information Idiochromatic: color by essential elements Allochromatic: color by trace or minor elements Moh’s Scale: Logarithmic. Talc, Gypsum, Calcite, Fluorite, Apatite, Orthoclase, Quartz, Topaz, Corundum, Diamond 2.2 fingernail, 3.2 copper penny, 5.5 glass plate, 6.5 steel file, 7.0 streak plate. Cleavages: -basal: 1 direction. eg. micas -feldspar cleavage: 2 at right angles -cubic: 3 at right angles. eg. galena -calcite cleavage: 3 at non right angles -octahedral: 4 directions. eg. fluorite, diamond -6 directions: eg. sphalerite -prismatic: multiple directions parallel to one cleavage. Parting: breakage from an unusual point of weakness in the crystal due to twinning plane or exsolution. Sheen: adularescence - reflection from microscopic inclusions schiller - reflection from inner layers iridescence - reflection from interference of inner layers play of color - diffraction of light through spheres of SiO2 in Opal Other: specific gravity: eg. Galena taste, smell: Halite, Sulphur feel: graphite magnetism: magnetite reaction with HCl: carbonates fluorescence: wolframite Lecture3:EarthChemistry crust - 36km from continents, 10-13 from ocean. Upper = sed. 95% ig rock. 10 miles down. upper mantle - 36-410km. Olivines + pyroxenes + garnet transition zone - 410-660km spinels + majorite lower mantle - 660-2600km. silicate perovskite + ferropericlase D’’ layer - 2600-2900km. post perovskite outer core - 2900-5100km. liquid iron allow inner core - 5100-6400km. solid iron. Earth Minerals 116 elements found in nature. 8 make up 99% of crust: O, Si, Al, Fe, Ca, Na, K, Mg -most crustal are O based. Some elements are concentrated in specific minerals (eg. Zr in Zircon ZrSiO4) -39% plag, 12% alkali feld, 12% quartz, 11% pyroxenes, 8% non silicates. . . . . ESS221 Study Notes Condensed Solid Solution ions substituting for each other in a mineral. Rarely find pure mineral states. Occurs as size of ions and site change composition, as well as temp/press changes. Lecture4:MineralChemistryandBonding Covalent > Ionic > Metallic > Van Der Waal’s Ions can form from light, heat, and electron exchange between atoms. HCP: Hexagonal closed packing - ABABABABAB CCP: Cubic closed packing - ABCABCABCABC along [111] Pauling’s Rules 1: Coordination Principle: Large radius atoms pack around a small radius atom in as tight a configuration as possible such that the small atom never rattles around in the space. The large radius atoms are always in contact with the small radius atom. Based on Radius ratios and angles from them. 2: Electrostatic Valency Principle: Bond strength (e.v.) = ZC/C.N In a stable crystal structure, the total strength of the valency bonds that reach an anion from all the neighbouring cations is equal to the charge of the anion Eg. Mg2+O6: SMg-O = 2/6 = 1/3 Eg. Si4+O4: SSi-O = 4/4 = 1 3: Sharing of Polyhedral Elements I The more corners that are shared between two polyhedrons, then the closer together the cations are. This destabilizes the structure because of cation-cation repulsion. 4: Sharing of Polyhedral Elements II In a crystal containing different cations, those of high valence and small coordination number tend not to share polyhedral elements with each other. 5: Principle of Parsimony The number of essentially different kinds of constituents in a crystal tends to be small. Very few types of contrasting cation-anion sites. Lecture5:LatticesandtheUnitCell lattice = grid /w motifs (single unit. eg. ion, atom) repeated regularly *which can be packed in a limited number of ways. They can be translated with an arbitrary origin. 2D unit cells: primitive or non-primitive (2 points +) ESS221 Study Notes Condensed Crystallographic Axes: A, B, C vs alpha, beta, gamma. Right Hand Rule: thumb is c, fingers are A, and arm is B along crystal with right hand. alpha(B,C). beta(A,C). gamma(A,B) Crystal Systems Bravais Lattices P = prim. F = face I = Body C = c-axis Lecture6:CrystallographicSymmetry Rotation: rotated on symmetry axis. 1, 2, 3, 4, 6 (360, 180, 120, 90, 60 degrees) Mirror Planes: reflection across mirror plane produces mirror image. ‘m’ ESS221 Study Notes Condensed Center of Symmetry: a point (eg. face) can be inverted and passed through center of crystal to appear on the other side. 1 bar symbol. Roto- Inversions: rotation and passing through crystal. 1 bar = center of symmetry. 2 bar = mirror plane. 3 bar = 120RI, 4 bar= 90RI and 6bar=60RI Point groups: Triclinic: 1, 1bar Monoclinic: 2, m, 2/m Orthorhombic: 222, 2mm, 2/m,2/m,2/m Lecture7:MillerIndicesandMore Crystallography Glide planes: translation and reflection Screw Axis: translation and rotation (like DNA) 14 Bravais lattice + 32 point group + 2 translation symmetry = 230 space groups. Miller Indices (hkl) = face {hkl} = family of faces [hkl] = direction of faces based on where a face intersects the axes. Usually use the number 1 to represent the faces when you have no coordinates. unit face = largest face that intersects all 3 axes. ESS221 Study Notes Condensed *hexagonal system has 4 axes [hkil] but one of the first three values are redundant, so you only need 3 to form a plane. Crystal form: a group of like crystal faces related by elements of symmetry. General form = faces intersect different axes at different lengths, which can describe multiple faces on a crystal. eg {111} Special form = all other forms present *faces that define the form need to have all positive intercepts. There are 48 total forms. 32 general ones. 10 special, 6 open. Zones set of faces parallel to a common direction (zone axis [hkl]) Lecture8:Crystallization Crystal Growth: atoms in solution no longer have enough energy to dissolve, so they form crystals. These grow based on available atoms. -> many form from water solutions (eg. quartz or NaCl) growth based on space freedom, time, and nutrients available. -> different minerals can grow simultaneously or sequentially on same rock Pseudomorphs: minerals get exposed to solutions, react, and recrystallize differently. Eg. Azurite can change to malachite, but maintain azurite appearance. ESS221 Study Notes Condensed Epitaxis: crystalline growth of one substance over another of different composition. Parallel Growths: intergrowths of same composition Twinning: Symmetrical intergrowth of 2+ of the same crystal formed by eroding during crystallization. -> contact twins - planar composition surface separates twins. eg. If twin plane is symmetric at 180 degrees, they are growing in opposite directions -> lamellar twins - repeated/continous contact twins (polysynthetic) Eg. Microcline tartan twins -> cyclic twins - repeats of contact twins in rotation at 30, 45, 60, 90 angles -> penetration twins - into and out of each other. eg. fluroite cubic or staurolite cruciform twins. Lecture9:ImagingMethods Qualititative = detective and identifying chemical constituents -Scanning Electron Microscopy -X-ray Diffraction Quantitative = %compositions -Electron Microprobe Analysis -X-ray D -Secondary Ion Mass Spectrometry -X-ray Fluorescence Electromagnetic Waves X-rays have photon energies between 100eV and -100eV. We use hard X-rays for diffraction between 1keV and -120 keV. wavelengths of X-rays are comparable to atom sizes, so this helps probe structural arrangements of atoms. X-ray Tube 1. Cathode emits electrons into vacuum 2. Anode collects them, making electrical flow beam 3. High V power source connects to cath/anode to accelerate ions 4. X-ray spectrum depends on anode material and voltage as anode rotates. X-ray diffractometers -when electrons have enough energy to dislodge from shell, X-ray spectra are produced. It can interpret a ratio of intensity Ka1:Ka2:Ka3 (a=alpha) Bragg’s Law: Used to interpret a X-ray diffraction data nλ = 2d sin(Ɵ) where: λ = wavelength of X-ray Ɵ = scattering angle ESS221 Study Notes Condensed n = order of diffraction peaks d = distance between successive atomic planes Parallel incident X-rays and scattering angles can help determine the distances Powder Diffraction PXRD is most widely use as powder sample gives more SA and useful when crystal is liquid suspended or in polycrystalline solids -can help define unit cell with a referencial lattice (hkl) -can detect purity -works best in isometric crystals -not helpful for multi-phase minerals -> check large peaks that don’t have overlaps Single Crystal Diffraction Shoots x-ray through fibreoptic taper that gets detected as visible light -> can tell us where atoms are located, and their bond positions and types, as well as symmetry and size of unit cell. Synchroton radiation and Neutron Diffraction - big ass expensive equipment that does stuff. Lecture10-LightandOpticalMicroscopy1 Light = waves + photons -> single wvlength = monochromatic -> we interpret vis. light as colors Wave theory: 1. visible light travels in a straight direction 2. It virates at angles to the direction of propagation, forming waves. frequency = number of waves that pass fixed point per unit time velocity = frequency x wvlength Refractive index: E = hν = hC/λ where E = energy, h = Planck's constant 6.62517 x 10-27 erg.sec, ν = frequency, C = velocity of light = 2.99793 x 1010 cm/sec, λ = wavelength RI = ratio of speed of light in a vacuum (C) to speed of light in a material that it passes through. Will always be above one since the speed will always be greater in a vacuum. If light strikes a material of a different RI, some light will reflect, and some will refract into the material. ESS221 Study Notes Condensed Snell’s Law: ni x sin (i) = nr x sin (r) Critical angle: refracted ray travels along the interface between two substances, at an angle Ic
More Less

Related notes for ESS102H1

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.