Diorite
Item
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Title
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Diorite
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Description
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Macroscopic: This hand sample is a grey to dark-grey intermediate intrusive igneous rock composed principally of plagioclase feldspar (typically andesine), biotite, hornblende, and/or pyroxene. This sample has a phaneritic texture which is common to diorite.
Microscopic: In planar light, the thin section sample clearly shows the phaneritic texture (Biotite and Hornblende and other various minerals show up as brown/green/light green or brown). In polarized light, the matrix reveals the plagioclase minerals. The majority of crystals (primarily biotite and hornblende) are anhedral - at one point being re-fractionated into the melt (this re-fractionation was cut short at eruption when the molten rock solidified); plagioclase crystals grew into the spaces between what remained of the hornblende and biotite crystals.
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Rights
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Lafayette College Department of Geology & Environmental Geosciences
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Identifier
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R-1825
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Date Created
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April 8, 2015
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Mediator
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Tamara Carley
