MINERALOGY
TASK#:1
Describe each mineral separately. Note the significant optical properties of each diagnostic mineral, the size and shape of each mineral, and the alteration (if any) of each mineral. Determine and record the percent of each mineral within the rock. Add rows is necessary.
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Mineral Name Size and Shape
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%
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Diagnostic Optical Properties
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Description
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Olivine
subhedral fractured
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18%
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2mblue; high birefrigence
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minor resorption
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opaques mineral microlites
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12%
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black in both ppl and cpl
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staining in parts; hematite
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plagioclase lath shaped zoned
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45%
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1 yellow; low birefrigence; 2cleavages; weak zoning; Alibite twinning
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Unaltered; showslight resorption
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Augite
small
subhedral
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30%
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inclined extinction
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Drawing/Photo
TEXTURAL DESCRIPTION (of thin section)
porphyritic texture is present, with large olivines and plagioclase phenocrysts in a fine grained groundmass. The groundmass has a glassy and black opaque groundmass of a very weak zoning
HAND SPECIMEN DESCRIPTION (if included)
ROCK HISTORY
This would have formed from a Hawaiian volcanic suite and at an intraplate location. The olivine phenocrysts crystallized first then the augite and plagioclase formed lastly. The presence of embayed olivine suggests resorption due to interaction with the melt.