lab1 - 1 Lab 1 Optical properties of common igneous and...

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1 Lab 1 Optical properties of common igneous and metamorphic minerals Introduction: Minerals in igneous and metamorphic rocks are either: 1- Essential minerals: these are the minerals whose presence, absence and abundance influence the rock name. They must be of igneous or metamorphic origin. Examples: quartz, feldspars, olivine, . .. etc. 2- Accessory minerals: are minerals that occur in minor amounts in igneous and metamorphic rocks, and are therefore not critical for giving the rock its name. Examples: apatite, zircon, sphene, . .. etc. 3- Secondary minerals: These are minerals that do not form by direct crystallization from the melt (in case of igneous rocks), or during the main (peak) metamorphic event, but at a later stage either during or after the cooling and crystallization. Although some secondary minerals in igneous rocks can be of igneous origin (e.g. hornblende formed by the deuteric alteration of pyroxene), many are not, and may form by weathering or hydrothermal alteration after the formation of the rock (e.g. calcite, chlorite, sericite,
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This note was uploaded on 02/28/2012 for the course GLY 421 taught by Professor Staff during the Fall '11 term at Marshall.

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lab1 - 1 Lab 1 Optical properties of common igneous and...

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