File:Rhyolitic perlite (Yellowstone, Wyoming, USA) (26613090897).jpg
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Summary
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| Description |
Rhyolitic perlite ("perlitic rhyolite") from the Quaternary of Wyoming, USA. (public display, Geology Department, Wittenberg University, Springfield, Ohio, USA) Small black areas = rhyolitic obsidian Gray-colored areas = perlite Light-colored areas = perlite, or possibly phenocrysts embedded in the original obsidian (if the latter, the obsidian would have been a vitrophyre - an obsidian with scattered crystals). Perlite is a scarce rock formed by hydrous alteration of some volcanic rocks. Perlites are hydrous volcanic glasses, usually having felsic chemistry (and so are rhyolitic in composition). The appearance varies, but includes the famous "Apache tears"-type of perlitized obsidian in the American southwest (e.g., <a href="https://www.flickr.com/photos/usageology/7978391111">www.flickr.com/photos/usageology/7978391111</a>). In such examples, the light-colored material around the black obsidian "Apache tear" cores is the perlite. Obsidian is unstable on geologic time scales and slowly crystallizes. Perlite is an early phase of this devitrification process. Perlitization occurs as the original obsidian takes on water (hydration). Locality: unrecorded/undisclosed site at Yellowstone, northwestern Wyoming, USA |
| Date | |
| Source | Rhyolitic perlite (Yellowstone, Wyoming, USA) |
| Author | James St. John |
Licensing
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/26613090897 (archive). It was reviewed on 10 October 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 01:50, 10 October 2019 | | 1,083 × 1,177 (1.27 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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