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| ANDESITE PORPHYRY (detail)
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Typical Minerals Minerals too small to identify (except phenocrysts, which here are amphibole). Composition will be from middle of Bowen's Reaction series, and include such minerals as Ca/Na plagioclase, amphibole, and biotite. |
Detail Description
This image is out of focus, but it shows well the light flashing off some of the elongate amphibole phenocryst cleavage faces, as well as amphibole without light flashes. In a photograph this is a hard feature to capture; typically the specimen has to be rotated under the microscope to see this. The same thing is true with many cleavages, or special features like plagioclase striations. So, the diagnostic features are often hard to capture in a rock, but here we can see it. If this were pyroxene it would typically not have this kind of shine. |
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| Last Update: 9/29/00 | e-mail: (Fichtels@jmu.edu) |