Henry
spending too much on rocks
Member since January 2013
Posts: 452
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Post by Henry on Dec 20, 2014 12:32:35 GMT -5
Hello all. So basically this was found at the very tip of the cliffs of Jade Cove, Monterey County. California. Being a former ancient beach 100,000 years ago before the sea-level lowered, (as I was told) a lot of the stuff is oxidized from the iron rich soil. My question is this: though being pretty run-of-the mill "Franciscan Complex" stuff, is this considered jasper or chert?? Thanks. Sidenote:picture is actually darker that what is visually perceived. It's actually rather orange.
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Orange
Dec 20, 2014 14:30:17 GMT -5
Post by adam on Dec 20, 2014 14:30:17 GMT -5
It seems to me, as I've always been on my own deciding the difference, I've found that jasper is not very translucent. Light can pass through the jasper a little and has a glow; makes patterns similar to agate, although difficult to recognize. It's pretty smooth mostly, feels nice to run your fingers against. I think I have some chert too, and what I can make a connection with your piece and ones I have seen, I've the opinion this appears like chert. Don't take take my word for it, this is just what I'm making out. Chert is more like sparkly, fine, weathered quartz-looking, smoother than jasper(sort of powdery). I'm still learning too. The distinctions are subtle to me, no matter how much I read I can't be sure of what catergory of rocks I have(probably a fourth of what I have I've not figured out. You just have to take a step back sometimes and recognize the key features of your's.
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Orange
Dec 21, 2014 6:01:42 GMT -5
Post by snowmom on Dec 21, 2014 6:01:42 GMT -5
the color make me think of K-Feldspar,
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,455
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Post by Sabre52 on Dec 21, 2014 9:05:33 GMT -5
The jasper- like materials from the Franciscan Formation are technically supposed to be a marine radiolarian chert. The marine sediments are infused with silica from deposits of siliceous radiolarian and diatom skeletons and sponge spicules, as opposed to jasper which gets it's silica from siliceous volcanic deposits like ash, perlite etc.....Mel
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Fossilman
Cave Dweller
Member since January 2009
Posts: 20,680
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Orange
Dec 21, 2014 10:44:35 GMT -5
Post by Fossilman on Dec 21, 2014 10:44:35 GMT -5
Nice colors..........Have you any slabs yet? Curious on what it cuts like!
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Orange
Apr 11, 2015 18:10:22 GMT -5
Post by stephan on Apr 11, 2015 18:10:22 GMT -5
It seems to me, as I've always been on my own deciding the difference, I've found that jasper is not very translucent. Light can pass through the jasper a little and has a glow; makes patterns similar to agate, although difficult to recognize. It's pretty smooth mostly, feels nice to run your fingers against. I think I have some chert too, and what I can make a connection with your piece and ones I have seen, I've the opinion this appears like chert. Don't take take my word for it, this is just what I'm making out. Chert is more like sparkly, fine, weathered quartz-looking, smoother than jasper(sort of powdery). I'm still learning too. The distinctions are subtle to me, no matter how much I read I can't be sure of what catergory of rocks I have(probably a fourth of what I have I've not figured out. You just have to take a step back sometimes and recognize the key features of your's. One definition I heard elsewhere isn't that accurate, but it is amusing: if you like it it's jasper, if you don't it's chert. ;-)
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,455
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Post by Sabre52 on Apr 11, 2015 18:20:59 GMT -5
Yeah, " chert" used to be the term we assigned just ole crap leaverite jasper that was brown, drab red, dull green or gray etc Not scientific but in the olden days, that's the way we called it....Mel
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Orange
Jun 1, 2015 11:09:05 GMT -5
Post by adam on Jun 1, 2015 11:09:05 GMT -5
Haha I finally understand it all now
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