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Rhyolite sample
Rhyolite sample
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Rhyolite sample
Rhyolite is an extrusive igneous rock with high silica content due to primarily being comprised of felsic minerals, such as quartz and plagioclase, but can occur in a number of shades. In some instances, they can have trace amounts of mafic minerals, like biotite, amphibole or pyroxene. Its composition is equivalent to that of granite but the two types of rocks differ from their formational processes and textures. Both are sourced from magmas of very similar composition, however granite crystallizes intrusively resulting in phaneritic and equigranular grains, whereas rhyolite cools rapidly extrusively during volcanic eruptions, typically resulting in an aphanitic texture. However, rhyolite can take up several forms depending on the cooling rate. For example, this particular sample crystallized gradually enough before surface exposure to form large phenocrysts but also has a high density of vugs, indicating gas content. Vugs are pockets that form from the entrapment of gases in the magma and are released upon bursting at the Earth's surface. The amount of gas content in a rhyolitic magma can be very influential on its cooling rate as the greater amount of gas, the more explosive the eruption and the faster the cooling rate. These can result in different classifications of rocks based on textural characterisitics, such as glassy obsidian or highly vesicular pumice rhyolites.
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Date
09/06/2018
Creator
Dolphin, Glenn
Digital Publisher
Calgary : University of Calgary
Location
Country
Canada
Municipality
City of Calgary
How can you use this image?
Permitted uses are outlined in License and Usage Rights. Usage Restrictions can only be waived by the copyright holder. Add to cart and make a request if you have any questions.
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In Copyright
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Conditions of Use
https://libanswers.ucalgary.ca/faq/199047
License URL
https://creativecommons.org/licenses/by/4.0/
License
CC BY 4.0
Attribution
Attribution
Rhyolite sample, 2018, (CU123330) by Dolphin, Glenn, is used under CC BY 4.0. Courtesy of Geoscience Images Collection, Libraries and Cultural Resources Digital Collections, University of Calgary.