Joseph Hoffman
off to a rocking start
Member since November 2020
Posts: 20
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Post by Joseph Hoffman on May 26, 2021 12:05:10 GMT -5
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Post by jasoninsd on May 26, 2021 14:14:49 GMT -5
I'd cut it and cab it! LOL That's a nice one. Tough call on the tumble. It's got that one fracture...so if it were me, I'd tumble it figuring that fracture line would stay. Really spectacular find!
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Post by rockpickerforever on May 26, 2021 15:06:51 GMT -5
I hope I'm wrong on this, but I don't think that is LSA. The banding on it is not precise enough, if that makes sense. If you have found them in the past, then you should know what I am saying.
I think it is some type of jasper. It is pretty coarsely grained, so will not take a shiny polish like a finely grained LSA would. It also looks to have cracks and pits.
This is simply my opinion, others may have a different take. But cut it, or tumble it if you'd like. Nothing ventured, nothing gained! Good Luck!
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Post by Drummond Island Rocks on May 26, 2021 16:10:01 GMT -5
Laker would not be my first guess for that one. Brown with swirls and found on Superior could be a form of Rhyolite. No harm in throwing it in the tumbler.
Chuck
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stefan
Cave Dweller
Member since January 2005
Posts: 14,095
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Post by stefan on May 26, 2021 16:21:51 GMT -5
Very hard to tell if it is a LSA. As rockpickerforever pointed out the banding looks imprecise and there appears to be a lot of undercutting going on. It also seems to be lacking the glassy appearance that most Agates have. Not to say that it could not be a very worn beat up specimen that has spent way too much time being beat down by glaciers, and contains a wonderful agate center. Guess they only way we will ever know is to cut it or tumble it! If it matters at all I would tumble it!
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rockstock
spending too much on rocks
Member since April 2019
Posts: 472
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Post by rockstock on May 26, 2021 17:01:04 GMT -5
Looks like stromatolite, stromaporoid or whatever those things are
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Post by Drummond Island Rocks on May 26, 2021 17:38:34 GMT -5
Looks like stromatolite, stromaporoid or whatever those things are That makes sense with the swirls. Mary Ellen Jasper that is found on Superior is a Stromatolite. So maybe this is another stromatolite variety. Chuck
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rewdownunder
spending too much on rocks
Member since March 2012
Posts: 357
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Post by rewdownunder on May 26, 2021 17:51:29 GMT -5
The rocks in the background all look like material found around Lake Superior but the "agate" just does not look like a LSA. If you cut it I think you will find it is a Precambrian siltstone of some type. There is a lot of this in outcrops in the Thunder Bay area just north of the border. I did my Geology grad work in Duluth and have seen this material before. It just does not have the luster and detail you find in LSA. Keep looking a laker that size would be quite a find.
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rockstock
spending too much on rocks
Member since April 2019
Posts: 472
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Post by rockstock on May 26, 2021 17:58:48 GMT -5
Couple swirls/banding I found, fossil stuff not agate
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Post by fernwood on May 26, 2021 21:29:04 GMT -5
I agree. Stromatolite. They can be found in some area of the Big Lake.
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rewdownunder
spending too much on rocks
Member since March 2012
Posts: 357
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Post by rewdownunder on May 27, 2021 11:57:06 GMT -5
Most stromatolites in that area are associated with banded iron formation like the Mary Ellen "jasper" and it would be very heavy, but There are some stromatolites in the UP to the east of you like the Kona Dolomite that could end up looking like that. Your going to have to cut it to take a close look at the pattern to know for sure. If it is a stromatolite cutting it will not devalue it. Find a local rock club and ask them to cut it for you or find someone with a water cooled tile saw It is not going to be hard to cut. There several rocks shops in the UP that may be able to ID it if it is a common local rock.
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Post by Rockindad on May 27, 2021 17:32:03 GMT -5
Agree with others that say It is likely not a LSA.
Most of the time we are not sure of what to do with a rock we tumble it in coarse for a cycle or two. Often it will reveal patterns, potential, help identify, etc. without losing too much material. Then the decision is made to keep it as a tumble, slab, window cut, not bother with, etc.
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Post by toiv0 on May 27, 2021 21:06:07 GMT -5
I don't think stromatolite. Technically Lakers can be found as far south as Kansas and as far west as Lincoln Nebraska. Most a gates banded or not in my area NE Minnesota are called lakers. So I guess my thoughts are if it is an agate and not a Ryolite or some other rock, and it was found around the lake I would call it a laker.
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Joseph Hoffman
off to a rocking start
Member since November 2020
Posts: 20
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Post by Joseph Hoffman on May 28, 2021 7:04:51 GMT -5
Thanks for all the discourse guys! My suspicions were that it wasn't an agate, but I had never seen anything that looks like this that isn't an agate. Regardless, I was very excited when I picked it up! Here's a (hopefully) real agate I found on the same day:
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Joseph Hoffman
off to a rocking start
Member since November 2020
Posts: 20
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Post by Joseph Hoffman on May 28, 2021 7:09:28 GMT -5
Does it feel heavy for it’s size? If so it’s probably an ironstone concretion. It is quite heavy.
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Post by rmf on May 28, 2021 9:05:05 GMT -5
Does it feel heavy for it’s size? If so it’s probably an ironstone concretion. It is quite heavy. Your initial picture is a Rhyolite. My son went to Houghton and I only had one opportunity to look for LSA when I was up there but I did find the best arkose ripplemark I have ever seen. After I retire I want to go up there and and spend some time when not competing with college parents for motel rooms and look for LSAs.
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stefan
Cave Dweller
Member since January 2005
Posts: 14,095
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Post by stefan on May 30, 2021 16:47:27 GMT -5
That second one is an Agate for sure!
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Post by stephan on May 30, 2021 23:36:43 GMT -5
Your initial picture is a Rhyolite. My son went to Houghton and I only had one opportunity to look for LSA when I was up there but I did find the best arkose ripplemark I have ever seen. After I retire I want to go up there and and spend some time when not competing with college parents for motel rooms and look for LSAs. Arkose ripplemark sounds like a great name for a band. Probably acid rock.
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