302-pp8 - UNIVERSITY OF SOUTH ALABAMA GY 302:...

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GY 302: Crystallography & Mineralogy GY 302: Crystallography & Mineralogy UNIVERSITY OF SOUTH ALABAMA Lecture 8: Native Elements Lecture 8: Native Elements
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Last Time 1. Mineral properties under XN (crossed Nichols/polars) 2. Mineral Classes/Properties 3. Native Elements; Chemistry & Crystallography (properties)
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B: Crossed Nichols (XN) 6) Extinction : occurs when the indicatrix aligns up with the polars and the entire crystal goes black (extinct). PPL PPL XN XN Optical Properties
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B: Crossed Nichols (XN) 7) Birefringence . This is the most important property of minerals under crossed polars. It is defined as the difference between the index of refraction of the minimum and maximum refractive indices of a mineral. For uniaxial minerals; n o –n e or n e -n o. For biaxial crystals; n a –n c or n c -n a . As far as you are concerned, you see pretty colours under XN Optical Properties
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Optical Properties
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B: Crossed Nichols (XN) 8) Optical Twinning . Same thing as physical twins whereby two or more crystals of a single mineral grow together in a mathematically predicable pattern (involves twin planes, twin axes etc). Optical Properties PPL XN
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B: Crossed Nichols (XN) 9) Zonation . Some minerals change their composition has they grow, particularly those that that form continuous series through solid solution during igneous processes (e.g., olivine, plagioclase). This can result in optical zonation. PPL PPL XN XN Optical Properties
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Today’s Agenda Native elements 1. Chemistry and Crystallography (properties) 2. Occurrences and Associations 3. Economics (resources, reserves, extraction) Featured Minerals: Gold and Diamonds
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Today’s Agenda Native elements 1. Mineral Classes/Properties 2. Chemistry and Crystallography (properties) 3. Occurrences and Associations 4. Economics (resources, reserves, extraction) Featured minerals: Gold, Diamonds
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Native Elements Copper Cu Isometric Gold Au* Isometric Silver Ag* Isometric Platinum
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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-pp8 - UNIVERSITY OF SOUTH ALABAMA GY 302:...

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