Timeline for A few questions about glass
Current License: CC BY-SA 3.0
4 events
| when toggle format | what | by | license | comment | |
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| Sep 11, 2017 at 5:16 | comment | added | uhoh | That's fascinating. Wow, devitrification is a thing! I'll go off now and read all about it, thank you! | |
| Sep 11, 2017 at 1:01 | comment | added | Knob Scratcher | No subduction required...(although stability in a museum display case is likely pretty good). Given the composition of obsidian, remember- it's not "glass" but technically a highly felsic polymer containing all of the elements that make it pretty close to silicic rhyolite in composition, it takes is some near-surface hydrothermal conditions to initiate the re-ordering of SIO4 tetrathedral framework to a more stable phase. Of course the question is how and why it even forms in an unstable state to begin with. Look up: "devitrification of geologic glasses" to see how I mangled my facts | |
| Sep 10, 2017 at 3:23 | comment | added | uhoh | How slowly? Is obsidian really "mineralogically unstable" near the surface, or is this only true at elevated temperatures and pressures after subduction? Could you add a supporting link or reference for this? Thanks! | |
| Sep 10, 2017 at 0:46 | history | answered | Knob Scratcher | CC BY-SA 3.0 |