302-pp2

# 302-pp2 - UNIVERSITY OF SOUTH ALABAMA GY 302:...

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GY 302: Crystallography & Mineralogy GY 302: Crystallography & Mineralogy UNIVERSITY OF SOUTH ALABAMA Lecture 2: More Symmetry Operations, Bravais Lattices Lecture 2: More Symmetry Lecture 2: More Symmetry Operations, Bravais Lattices Operations, Bravais Lattices

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Last Time ± ± A long winded introduction A long winded introduction ± ± Introduction to crystallography Introduction to crystallography ± ± Symmetry Symmetry
Crystal Systems The 6 (or 7) Crystal Systems. Plagioclase " \$ ( 90° a b c Triclinic 6 Gypsum, Orthoclase " = \$ =90° , ( 90° a b c Monoclinic 5 Aragonite, Staurolite " = \$ = ( =90° a b c Orthorhombic 4 Quartz, Calcite " = \$ =120° , ( =90° a= a 1 =b c Trigonal 3b Apatite " = \$ =120° , ( =90° a 1 = a 2 =a 3 c Hexagonal 3a Zircon " = \$ = ( =90° a = b c Tetragonal 2 Halite, Galena, Pyrite " = \$ = ( =90° a = b = c Cubic 1 Mineral examples Angles between axes Axes Crystal System

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Crystal Systems In order to fully understand how crystals are “put together”, We need to reconsider symmetry. In the last lab, we examined 3 symmetry operations: 1) Reflection (mirror planes)
Crystal Systems In order to fully understand how crystals are “put together”, We need to reconsider symmetry. In the last lab, we examined 3 symmetry operations: 1) Reflection (mirror planes) 2) Rotation (2, 3, 4, 6 fold axes)

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Crystal Systems There are two other operations that we did not have a chance to discuss at the start of lab 1 (e.g., rotoinversion) 1) Reflection (mirror planes) 2) Rotation (2, 3, 4, 6 fold axes) 3) Inversion Center of Inversion
Crystal Systems 1) Reflection (mirror planes) 2) Rotation (2, 3, 4, 6 fold axes) 3) Inversion 4) Translation 5) Screw Rotation 6) Glide Rotation 7) Rotoinversion Basic symmetry operations Compound symmetry operations

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Today’s Agenda 1. Rotoinversion 2. Translational Symmetry 3. Bravais Lattices
Symmetry in Crystals Rotation axes: http://www.cartage.org.lb 2-fold Rotation Axis - If an object appears identical after a rotation of 180 o , that is twice in a 360 o rotation, then it is said to have a 2-fold

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## This note was uploaded on 02/05/2012 for the course GLY 302 taught by Professor Staff during the Spring '11 term at S. Alabama.

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302-pp2 - UNIVERSITY OF SOUTH ALABAMA GY 302:...

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