Deleted
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Post by Deleted on Jan 8, 2017 21:08:33 GMT -5
In another conversation in another venue, someone with significant knowledge indicated that obsidian such as Davis creek OB is actually granite, chilled too fast for crystal formation. ETA is the chemistry the same for both materials? Anybody know how I may research this? Or have specific knowledge? 1dave Sabre52
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Post by Deleted on Jan 8, 2017 21:12:36 GMT -5
This is counter intuitive for me.
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Fossilman
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Post by Fossilman on Jan 9, 2017 11:09:20 GMT -5
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Post by 1dave on Jan 9, 2017 11:53:42 GMT -5
Modern volcanics begin with a basalt composition, but as they melt toward the surface they cool as they melt the granite composition above, Olivine crystallizes and drops out and the magma slowly changes to a granite composition. If it never reaches the surface it cools into granite. If there is lot of water in it it explodes sending ash in the air. With lower water content it pours onto the surface as "perlite." With even less water it quickly cools as "obsidian." even less water, as rhyolite. Granite Composition: en.wikipedia.org/wiki/ObsidianApache Tear in Perlite matrix: www.waymarking.com/waymarks/WMB0QD_Apache_Tears_near_Superior_Arizona
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Post by vegasjames on Jan 9, 2017 15:18:26 GMT -5
In another conversation in another venue, someone with significant knowledge indicated that obsidian such as Davis creek OB is actually granite, chilled too fast for crystal formation. Anybody know how I may research this? Or have specific knowledge? 1dave Sabre52 That does not make any sense. First of all obsidian is formed from rapid cooling preventing crystalline structure. This can even be done with metals to make metallic glasses. But granite has a crystal structure. And granite has quartz, as where obsidian does not.
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Post by 1dave on Jan 9, 2017 15:26:53 GMT -5
In another conversation in another venue, someone with significant knowledge indicated that obsidian such as Davis creek OB is actually granite, chilled too fast for crystal formation. Anybody know how I may research this? Or have specific knowledge? 1dave Sabre52 That does not make any sense. First of all obsidian is formed from rapid cooling preventing crystalline structure. This can even be done with metals to make metallic glasses. But granite has a crystal structure. And granite has quartz, as where obsidian does not.
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Post by vegasjames on Jan 9, 2017 18:43:20 GMT -5
That does not make any sense. First of all obsidian is formed from rapid cooling preventing crystalline structure. This can even be done with metals to make metallic glasses. But granite has a crystal structure. And granite has quartz, as where obsidian does not. Silicon dioxide exists in various forms. Not just quartz.
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Post by 1dave on Jan 9, 2017 22:22:12 GMT -5
Silicon dioxide exists in various forms. Not just quartz. And?
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Post by Deleted on Jan 9, 2017 22:56:33 GMT -5
Silicon dioxide exists in various forms. Not just quartz. And? James, I think that my original question was answered in the affirmative. Both publicly and privately from one elegant and polite member that didn't want to answer publicly. The components of granite are in the obsidian, just supercooled like the metals you describe. Had the obsidian had the opportunity for a slower cool, the crystals would have formed into the rock we call granite.
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Post by Deleted on Jan 9, 2017 22:56:55 GMT -5
Thanks 1dave mystery member and fossilmanInteresting concept. The magma of our planet is relatively homegenous. Just the cooling rates in various settings make the difference.
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jamesp
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Post by jamesp on Jan 10, 2017 1:24:52 GMT -5
Quartz glass and silica are tricky studies.
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Post by vegasjames on Jan 10, 2017 4:35:17 GMT -5
Silicon dioxide exists in various forms. Not just quartz. And? And as said before "granite has quartz, as where obsidian does not". Just because obsidian is primarily silica that does not mean the silica is in the form of quartz.
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Post by vegasjames on Jan 10, 2017 4:38:50 GMT -5
James, I think that my original question was answered in the affirmative. Both publicly and privately from one elegant and polite member that didn't want to answer publicly. The components of granite are in the obsidian, just supercooled like the metals you describe. Had the obsidian had the opportunity for a slower cool, the crystals would have formed into the rock we call granite. To me that would be stretching it. That is like claiming since methane, propane, hexane, etc. all contain the same components of carbon and hydrogen they must all be the same thing. If I recall right by definition a granite also has visible crystal structure. Obsidian being a glass does not.
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Post by 1dave on Jan 10, 2017 8:51:04 GMT -5
SiO 2 is forced into many polymorphs depending on heat and pressure, but they are still SiO 2. Here we are considering the constituents of Granite, Rhyolite, and Obsidian, Not what polymorphs those minerals happen to be in. There are many kinds of granite depending on slight changes of amounts depending on what minerals exist in different parts of the earth, but they are all classified as granite, a rock - not a mineral. All three types of rocks consist of nearly the same minerals. The main difference is the cooling rate.
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jamesp
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Post by jamesp on Jan 10, 2017 9:59:18 GMT -5
Hell, they just dialed in on Moganite fairly recently. Silica will continue to befuddle scientists. Cause debate. SiO2 hath many personalities.
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Deleted
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Post by Deleted on Jan 10, 2017 10:07:45 GMT -5
James, I think that my original question was answered in the affirmative. Both publicly and privately from one elegant and polite member that didn't want to answer publicly. The components of granite are in the obsidian, just supercooled like the metals you describe. Had the obsidian had the opportunity for a slower cool, the crystals would have formed into the rock we call granite. To me that would be stretching it. That is like claiming since methane, propane, hexane, etc. all contain the same components of carbon and hydrogen they must all be the same thing. If I recall right by definition a granite also has visible crystal structure. Obsidian being a glass does not. The claim and my question was about chemistry. Same chemistry different t structure.
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jamesp
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Post by jamesp on Jan 10, 2017 10:22:49 GMT -5
Most Common Mineral of the Continents
The most common mineral of the Earth's continents - the world we spend our time in - is quartz, the mineral SiO2. Nearly all the sand in sandstone, in the deserts of the world and on its riverbeds and beaches is quartz. Quartz is also the most common mineral in granite and gneiss, which make up the majority of the deep continental crust.
Most Common Mineral of the Crust
If you consider it as one mineral, feldspar is the most common mineral and quartz comes in second, especially when you consider the whole crust (continental plus oceanic). Feldspar is called a group of minerals only for the convenience of geologists. The seven major feldspars blend smoothly into each other, and their boundaries are arbitrary. Saying "feldspar" is like saying "chocolate-chip cookies," because the name embraces a range of recipes.
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jamesp
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Post by jamesp on Jan 10, 2017 13:26:58 GMT -5
I love Texas quartz. And S.GA./N.FL. quartz.
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Post by vegasjames on Jan 10, 2017 15:29:14 GMT -5
To me that would be stretching it. That is like claiming since methane, propane, hexane, etc. all contain the same components of carbon and hydrogen they must all be the same thing. If I recall right by definition a granite also has visible crystal structure. Obsidian being a glass does not. The claim and my question was about chemistry. Same chemistry different t structure. My point still stands. Same chemistry, different structure still makes a completely different thing. Let me put it this way. If I write the chemical formula C 6H 12O 6 am I referring to glucose, fructose, mannose, tagatose or galactose? All have the same exact formula C 6H 12O 6 as do some other sugars yet they all have different chemical structures making them all different compounds with different properties.
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Post by 1dave on Jan 10, 2017 16:54:32 GMT -5
The claim and my question was about chemistry. Same chemistry different t structure. My point still stands. Same chemistry, different structure still makes a completely different thing. Let me put it this way. If I write the chemical formula C 6H 12O 6 am I referring to glucose, fructose, mannose, tagatose or galactose? All have the same exact formula C 6H 12O 6 as do some other sugars yet they all have different chemical structures making them all different compounds with different properties. But all made of the same exact stuff.
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