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Post by grumpybill on May 29, 2019 9:40:48 GMT -5
A grandson found this in the $/lb. pile outside the local rock shop, so it's impossible to know where it came from. The crinkled texture continues on all surfaces, so it's not likely the rounded shape was caused by erosion. Scratch test with tool steel on a relatively smooth area left a metallic streak and maybe a very shallow scratch. No magnetic attraction. Any thoughts on what it is?
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Post by MsAli on May 29, 2019 9:59:49 GMT -5
No clue but its really neat
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Post by grumpybill on May 29, 2019 10:24:09 GMT -5
I should have mentioned the stone shown above is ~3" long. Also that my youngest granddaughter insists it's a dinosaur turd. This one (found at the same time) is almost flat and ~1" across the short dimension. (Sorry for the blurry image, but I was too lazy to change out the macro lens.)
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Post by MsAli on May 29, 2019 10:38:10 GMT -5
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Post by grumpybill on May 29, 2019 11:46:23 GMT -5
The Gobi in your link has rounded bumps, whereas these have distinct ridges like I've never seen in an agate. I've seen stones with this texture before. Not sure where, though.
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on May 29, 2019 12:34:21 GMT -5
I've seen similar textures on agate nodules that had eroded out of vesicular basalt. Basically bubbles that had been compressed by pressure before being filled with agate. Really interesting - too interesting to cut into them - and like small, natural sculptures.
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Post by grumpybill on May 29, 2019 13:02:14 GMT -5
I have no inclination to open one. Going by Kentucky windage - i.e. holding it in my hand and making a wild assed guess - they seem to have more mass/specific gravity than agate. More like iron, which is why I tried a strong magnet on them.
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Post by grumpybill on Jun 1, 2019 10:22:41 GMT -5
The rock shop where these came from is owned by a couple who are geologists, so I stopped back to today with the larger piece to see what they had to say. Neither geologist was there, but I noticed they have similar, slightly larger, pieces for sale inside. They were labeled as "iron concretions". I didn't have a magnet with me, but I've tested my pieces with both a large strong ceramic magnet and a powerful NeoD magnet. I doubt they have any iron content.
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