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Post by tandl on Jan 28, 2012 9:58:33 GMT -5
We have had the discussion of what the difference is of agate,jasper,flint,chalcedony,chert... They are all chert . en.wikipedia.org/wiki/Chert
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mjflinty
spending too much on rocks
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Member since September 2011
Posts: 358
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Post by mjflinty on Jan 28, 2012 11:53:27 GMT -5
Technically, they are all SiO2 plus other elements that give them color. At least, that's what I tell my students.
Michael
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Post by Toad on Jan 28, 2012 22:39:31 GMT -5
Well hell, that makes it easy.
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,472
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Post by Sabre52 on Jan 28, 2012 22:56:27 GMT -5
Nope in ain't easy at all *L*. Chert/flint are associated with marine deposits and the silica that forms that sort of quartz gem comes from organic sources like sponge spicules, diatoms, radiolarian skeletons etc. Agate and jasper come from silica associated with volcanic deposits. The wiki guy is thinking of "chert" as an incorrect common name for poor quality jasper, flint etc. Problem with Wiki is anyone can post nonsense based on what they think they know. The whole subject is actually very complicated and we've gone over it all before. It's common names that cause most the confusion as there are sedimentary agates and igneous associated agates, jaspers that are rhyolites, silicified volcanic sediments called jaspers, cherts misnamed things like like Morgan Hill Jasper, Ocean Jasper that's more of an orbicular agate etc etc. We collectors call lots of translucent chalcedony with various patterns and inclusions agate, whereas purists call only the banded nodules agate. It's actually pretty mind boggling *L* Mchael is right about the basics though, all microcrystalline SIO2 infused with various impurities....Mel
I guess I should clarify my statement too. What the guy has posted is not nonsense but some sections are oversimplified because his discussion omits much info about deposits associated with igneous rocks which is where much of our collectable stuff comes from and he sort of omits much of the confusion caused by common or trade names. I guess I'd say his discussion re: agate and jasper ( since he decided to include them) is incomplete especially from the standpoint of us lapidary nerds, but relatively complete with regard to flint/chert *L*.
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