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Post by amygdule on Oct 1, 2021 16:54:38 GMT -5
Here's a pic of a Green Jasper nodule weathering out of the basalt on the Oregon Coast.
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Post by stephan on Oct 1, 2021 17:20:15 GMT -5
Actually, serpentine, nephrite and jadeite are very much related. The depth of subduction changes the chemical make-up. I got this information first-hand from two geologists. One (Donald Dupras) worked for USGS and literally wrote the book on California jade. The other (Eldridge Moores, now deceased) taught geology for UC Davis and wrote multiple books on California geology. The first was a member of our rock club, the second led educational outings throughout California. Both were respected experts in their fields That's the way I understand it at well (the part About depth of serpentine in subduction zones). One other weird thing about jadeite, is that the structure changes from fibrous to granular, making it harder, but less tough than nephrite. Nature never ceases to amaze. As for the structure of chert, jasper, etc. cryptocrystalline is synonymous with microcrystalline, giving lots of fracture "choices," depending on the nature of the shear/stress applied to it, as can be seen in brecciated jasper. My choice of the word "cleavage" wasn't correct. I should have said it can fracture in a manner resembling perfect cleavage. It is obsidian (glass) that has no crystal structure.
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Post by stephan on Oct 1, 2021 17:34:48 GMT -5
I like this in the comments section of the first link, as it seems pretty consistent with popular use: "Jasper" is a good example of a name traditionally applied to a variety of different materials, making it more of a lapidary term than a definable varietal name. That way it also covers the rhyolite "jaspers" which add yet another twist that neither the main article nor the comments even touch. Other than that, the is always the classic, "if you like it, it's jasper, if you don't it's chert."
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gemfeller
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Post by gemfeller on Oct 1, 2021 18:01:20 GMT -5
This has nothing to do with the ID but Nephrite and Jadeite are two different minerals. Nephrite is an amphibole and Jadeite is a pyroxene. They are not related other than they are both found as green fine grain rocks. Without a thin section and microscope you can not tell the difference. Chalcedony is a cryptocrystalline form of quartz as it has no crystal structure it can not have cleavage by definition but that is not to say it can not break in flat surfaces. I am going to stick with "pretty green rock" I do not know of any nondestructive tests that tell us a lot more without having the rock in my hand. Actually, serpentine, nephrite and jadeite are very much related. The depth of subduction changes the chemical make-up. I got this information first-hand from two geologists. One (Donald Dupras) worked for USGS and literally wrote the book on California jade. The other (Eldridge Moores, now deceased) taught geology for UC Davis and wrote multiple books on California geology. The first was a member of our rock club, the second led educational outings throughout California. Both were respected experts in their fields Very sorry to hear Moores is deceased. His travels with John McPhee and his insights on California geology in McPhee's book "Assembling California" were memorable.
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JR8675309
freely admits to licking rocks
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Post by JR8675309 on Oct 1, 2021 18:08:36 GMT -5
That's where I recognize that name, John McPhee books!
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JR8675309
freely admits to licking rocks
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Post by JR8675309 on Oct 1, 2021 18:13:54 GMT -5
amygdule and stephan you have given me a lot of material to think about. I've read that jasper vs flint vs chert before, but as I gather more rocks, I tend to reread it to cement things in my mind. Each new rock, for me anyway, presents a new learning opportunity. Being on the S OR coast this past weekend, with all of the green material (and serpentine and asbestos worries) I was out of my element. I learned a lot though.
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Post by stephan on Oct 1, 2021 18:39:03 GMT -5
Actually, serpentine, nephrite and jadeite are very much related. The depth of subduction changes the chemical make-up. I got this information first-hand from two geologists. One (Donald Dupras) worked for USGS and literally wrote the book on California jade. The other (Eldridge Moores, now deceased) taught geology for UC Davis and wrote multiple books on California geology. The first was a member of our rock club, the second led educational outings throughout California. Both were respected experts in their fields Very sorry to hear Moores is deceased. His travels with John McPhee and his insights on California geology in McPhee's book "Assembling California" were memorable. Yes, he passed a few years ago, this month. He was a local treasure. Hikes with him were amazing. He could make a large group feel like a one-on-one, and had an ability to make complex information very understandable.
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Post by stephan on Oct 1, 2021 18:47:55 GMT -5
amygdule and stephan you have given me a lot of material to think about. I've read that jasper vs flint vs chert before, but as I gather more rocks, I tend to reread it to cement things in my mind. Each new rock, for me anyway, presents a new learning opportunity. Being on the S OR coast this past weekend, with all of the green material (and serpentine and asbestos worries) I was out of my element. I learned a lot though. Walk softly and carry a large spray bottle.... (apologies to Teddy, and to West Africa)
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gemfeller
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Post by gemfeller on Oct 1, 2021 20:14:13 GMT -5
Very sorry to hear Moores is deceased. His travels with John McPhee and his insights on California geology in McPhee's book "Assembling California" were memorable. Yes, he passed a few years ago, this month. He was a local treasure. Hikes with him were amazing. He could make a large group feel like a one-on-one, and had an ability to make complex information very understandable. I had a geology professor like that. He had a huge impact on my thinking and development. In fact, he changed my life by hugely expanding my mental vistas. It's amazing what one brilliant teacher can pass on to others.
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JR8675309
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Post by JR8675309 on Oct 1, 2021 22:05:09 GMT -5
Very sorry to hear Moores is deceased. His travels with John McPhee and his insights on California geology in McPhee's book "Assembling California" were memorable. Yes, he passed a few years ago, this month. He was a local treasure. Hikes with him were amazing. He could make a large group feel like a one-on-one, and had an ability to make complex information very understandable. I am sorry you lost someone who not only shared that common interest but who also could convey his expertise to his audience. Great teachers and mentors can be a rare breed.
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JR8675309
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Post by JR8675309 on Oct 2, 2021 8:49:52 GMT -5
Another green rock from S OR Coast. This one is translucent. What do you think? Outside Flipped over Next section Backlight
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JR8675309
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Post by JR8675309 on Oct 5, 2021 14:18:56 GMT -5
@jadedvision thanks for the assessment. Late reply, but I'm appreciative! So that's exactly was I was trying to avoid doing... (cutting serpentine). Is there a sure fire way to ID it? Something I'm missing? I have quite a few rocks that I brought home... some are the tri color red Jasper/green/"white" from Chetco river. I've seen posted that these are a Jasper mix and if they have serpentine I don't want to cut them. Tumbling also seems potentially hazardous.
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Post by jasoninsd on Oct 5, 2021 14:30:23 GMT -5
@jadedvision thanks for the assessment. Late reply, but I'm appreciative! So that's exactly was I was trying to avoid doing... (cutting serpentine). Is there a sure fire way to ID it? Something I'm missing? I have quite a few rocks that I brought home... some are the tri color red Jasper/green/"white" from Chetco river. I've seen posted that these are a Jasper mix and if they have serpentine I don't want to cut them. Tumbling also seems potentially hazardous. I just slabbed, trimmed, and cabbed a piece of Serpentine...and I feel just tindnowoudhsllw!
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Post by amygdule on Oct 5, 2021 15:44:22 GMT -5
jasoninsdDid you shave your beard and wear a gasmask ?
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Post by jasoninsd on Oct 5, 2021 16:18:41 GMT -5
jasoninsd Did you shave your beard and wear a gasmask ? That definitely looks like a picture of me 25 years ago! LOL No, I didn't shave the beard...but I'm going to have to shortly...my wife keeps telling me I'm starting to look like a crazy mountain man! I tell her I figure looking like one is better than acting like one! (She doesn't find as much humor in it as I do! LOL)
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Post by stephan on Oct 5, 2021 23:44:27 GMT -5
@jadedvision thanks for the assessment. Late reply, but I'm appreciative! So that's exactly was I was trying to avoid doing... (cutting serpentine). Is there a sure fire way to ID it? Something I'm missing? I have quite a few rocks that I brought home... some are the tri color red Jasper/green/"white" from Chetco river. I've seen posted that these are a Jasper mix and if they have serpentine I don't want to cut them. Tumbling also seems potentially hazardous. If you’re not cutting or grinding dry, it’s not really a problem. Silica dust is problematic too. The operative word being dust. If it’s wet, it’s mud, not dust. Also note that @jadedvision said, “a pretty solid one.” That makes it far less hazardous. The ones to worry about are the ones that look hairy: IMG_1227_Chrysotile asbestos specimen (yard-rock) by sdttds, on Flickr or worse: IMG_5904_Asbestos by sdttds, on Flickr amygdule jasoninsd The vintage gas mask pic is killing me. Guess what was used as the filtering material. Riebeckite — one of the most hazardous forms of asbestos.
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JR8675309
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Post by JR8675309 on Oct 7, 2021 15:24:30 GMT -5
Thanks! I'm curious, what are the inclusions in the rock I cut? They look silver.
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