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⇒Link to 3D rotatable image of this rhyolite porphyry This rhyolite porphyry comes from Chafee County, Colorado. The hand specimen is not red-colored like the previous two rhyolite samples because the feldspars are not hematitic.
Type Igneous Rock Texture Porphyritic Origin Extrusive/Volcanic Chemical Composition Felsic Color Light Green Mineral Composition Potassium Feldspar, Quartz, Sodium Plagioclase, Biotite, Hornblende Miscellaneous Potassium Feldspar and Quartz Phenocrysts in an aphanitic (fine-grained) groundmass Tectonic Environment Convergent Boundary – Andean-type subduction zones, intracontinental hot ...
Rhyolite Porphyry: Several specimens of rhyolite porphyry, each about three inches across. Click the image to enlarge. Eruptions of granitic magma can produce rhyolite, pumice, obsidian, or tuff. These rocks have similar compositions but different cooling conditions. Explosive eruptions produce tuff or pumice.
Samples of typical rhyolite porphyry from the Utley quarry showing dark lustrous quartz phenocrysts and pink to white K feldspar phenocrysts in a black matrix, which was initially volcanic glass, now devitrified.
29 Αυγ 2022 · Rhyolite is a light-colored, silica-rich extrusive igneous rock with a fine-grained to glassy texture but more often a porphyritic texture. The porphyritic texture is where larger crystals or phenocrysts are scattered in a finer-grained or glassy matrix.
Rhyolite is an extrusive igneous rock, formed from magma rich in silica that is extruded from a volcanic vent to cool quickly on the surface rather than slowly in the subsurface. It is generally light in color due to its low content of mafic minerals, and it is typically very fine-grained (aphanitic) or glassy. [5]
13 Μαρ 2023 · Rhyolite is felsic igneous extrusive rock and it is a fine-grained and dominated by quartz (>20%) and alkali feldspar (>35%).Due to the high silica content, rhyolite lava is very viscous. It is often difficult to identify rhyolites without chemical analysis due to their glassy groundmasses.
