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Porphyry
Porphyry
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Samples
Conceptually similar
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Lake at Saskatchewan Glacier
Porphyry
Porphyry is a texture assigned to igneous rocks that contain larger grained crystals within a finer-grained aphanitic matrix. These crystals are usually feldspars or quartz and are called phenocrysts. The phenocrysts in this sample are orthoclase feldspar, also known as potassium feldspar. The formation of this type of rock is due to variable cooling rates of the magma. Initially, the magma cooled slowly deeper down in the mantle, allowing coarse crystals to form. As the rock rose more rapidly and broke to the surface, the fine-grained matrix was formed to surround the larger crystals as the cooling rate rapidly increased closer to the surface. The fine matrix and coarse phenocrysts are often of the same composition.
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Digitized Date
09/06/2018
Creator
Dolphin, Glenn
Unique identifier
CU1STO6875
Location
Country
Canada
Province
Alberta
Municipality
City of Calgary
How can you use these images?
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.
Copyright Status
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
"Porphyry", unknown date, (CU1STO6875) by Dolphin, Glenn. Courtesy of Geoscience Images Collection, Libraries and Cultural Resources Digital Collections, University of Calgary.