Detail
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| RHYOLITE PORPHYRY
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Typical Minerals Minerals too small to identify (except phenocrysts, which here are orthoclase). Composition will be from bottom of Bowen's Reaction series (i.e. felsic). |
Description
A fine grained (aphanitic) igneous rock, white, light gray, pink, to dark in color. Orthoclase phenocrysts are present in this specimen. Color is such a poor indicator of rock identification in most cases, that it can only be a first approximation. Here, however, the orthoclase phenocrysts put it in the felsic range, although without knowing the quartz content we do not know if a phaneritic variety would be syenite or alkali granite. |
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Tectonic Association
Rhyolite, as with all felsic rocks, is found on continents, ejected from volcanoes. Tectonic Cross Section - pdf version
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| Last Update: 9/29/00 | e-mail: (Fichtels@jmu.edu) |