Monzonite (R1822)
Item
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Title
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Monzonite (R1822)
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Description
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Location: Silverton Calorado
Geologic Age: Miocene
Macrodescription: A purplish-gray rock consisting chiefly of plagioclase, orthoclase, and greenish hornblende with small amounts of quartz
Heterogranular texture with a few large cloudy orthoclase crystals with poikilitic plagioclase and mafic inclusions. Some potash feldspar has rims of granophyre which also forms interstitial patches. Dominant plagioclase ranges in size considerably and shows gradation zoning. Augite is partly or wholly uralitized to very weakly pleochroic green hornblende. Biotite is in part chloritized. Coarse granular magnetite is common; apatite and zircon are rare.
