NevadaBill
fully equipped rock polisher
Member since January 2019
Posts: 1,332
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Post by NevadaBill on Mar 24, 2019 15:29:23 GMT -5
Good day! I am hoping to get some idea of how these rock(s) were created. I had put this in another post an hour ago, along with others, but when I hit "Create Thread" just now, I got a Cloudflare error, and lost about 45 minutes worth of my work. So here goes .. again. I found this (and other rocks) on the banks of the Colorado River, Nevada. I call them the Waterline rocks. They are harder and smooth. Not Jasper hard though. They are like potatoes that got many lines on them. I have not cut one open to see what the insides look like. I will polish the smaller ones. I think they will take a shine. But I believe them to be a common rock, but I have not really noticed this kind before. The big one is the size of a football. So far I have not stumped anyone with my rocks. I am hoping that someone might be familiar with these rocks. Thank you for your help!
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fuss
spending too much on rocks
Member since October 2018
Posts: 250
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Post by fuss on Mar 24, 2019 22:46:30 GMT -5
sedimentary rocks, possibly sandstone. Dry photos and a hardness/scratch test would be helpful.
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Post by MsAli on Mar 25, 2019 8:39:10 GMT -5
I would say sandstone, tumbled naturally by the water
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Post by fernwood on Mar 25, 2019 8:52:07 GMT -5
Looks almost the same as some of my so called Baraboo Quartzite. They are found on the banks of Devil's Lake and in the Blue Hills regions of WI.
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NevadaBill
fully equipped rock polisher
Member since January 2019
Posts: 1,332
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Post by NevadaBill on Mar 26, 2019 8:47:26 GMT -5
Interesting. Yes, fernwood, this does have features in common with Baraboo Quartzite, which you mentioned. I am willing to bet that Sandstone is the correct guess. Also, I examine the big one more closely (which is kind of cracked on one end), and the lines go all of way through the rock. They aren't surface stains as I once though. Which makes this even more strange. I'll post dry pictures, and try to scratch 'em up real good for a hardness test. Thanks all for chiming in!
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NevadaBill
fully equipped rock polisher
Member since January 2019
Posts: 1,332
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Post by NevadaBill on Mar 26, 2019 16:45:11 GMT -5
All right, fuss. Here is what one looks like dried and cut open. This is one of the smaller ones, but the bigger ones are made of the same stuff. I can't seem to scratch it with a knife. But I can leave a lead pencil looking mark, which comes off with cloth & water. You can <right-click> / Open in new Tab to get a bigger picture. Or I can post blown up ones. I really would like to know how this one is made. Especially since the lines are not just water marks left on the outside. They are formed in layers. No clue. It is less grainy than some of the others. And I have some really outstanding versions of these rocks too. I hope one will polish. I am going to tumble a couple soon. Thank you for your help, if you know.
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thedude
off to a rocking start
Member since November 2019
Posts: 5
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Post by thedude on Nov 26, 2019 11:55:41 GMT -5
Looks to be BIF- Banded Iron Formation.
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NRG
fully equipped rock polisher
Member since February 2018
Posts: 1,630
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Post by NRG on Dec 1, 2019 18:46:09 GMT -5
I vote against banded iron formation.
I suggest googling "mylonized granite" if it's harder than sandstone.
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Post by rmf on Dec 4, 2019 15:42:08 GMT -5
Way to go fernwood!! Image #2 does indeed look like Baraboo Quartzite. In image #2 you can see the layers of coarser grains and then finer grains which give an indication that the water was moving faster at one time than another. The glacier moved Baraboo quartzite (about 5000" thick of it) to the south and west but I do not know how far. I have found it in northern Missouri, Iowa, IL, WI and KS. Do not know if it would make it to the Colorado River. It would be interesting if you could get a university to do a spectrographic analysis to see if the trace elements matched Baraboo quartzite. None the less it is quartzite. Not sure about some of the others though.
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Post by nowyo on Dec 9, 2019 6:27:23 GMT -5
Just saw this post. I'm going to have to agree with Scott, without actually looking at the rocks. Have some similar stuff out in the yard, found in shear zone associated with detachment faults. Nevada has multiple detachments, typically associated with metamorphic core complexes.
Russ
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Post by fernwood on Dec 9, 2019 6:56:44 GMT -5
I found some BQ in SW North Dakota. Gotta love terms applied to specific rocks in specific locals. The ND finds would indicate that BQ could have traveled to the Colorado River. It just might have a different name. Here are comparison photos of some BQ I gathered in NW WI. It is all over the place. Piles of it up to 6' boulder size. The County harvests it off ATV trails. Then uses it for fill along boat landings in the County forest. The largest rock is about 10". These received positive ID from a UW Geologist, in person. Please excuse the green areas. These rocks are on my deck. The green areas are slime, lol.
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fuss
spending too much on rocks
Member since October 2018
Posts: 250
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Post by fuss on Dec 9, 2019 11:06:25 GMT -5
Fernwood, I'm thinking what you found in ND is Sioux quartzite rather than quartzite from Baraboo WI.
There are several quartzite occurrences in northern WI as well, you may have found some Barron or flambeau ridge quartzite in northern WI. Though the Baraboo quartzite is used as decorative stone, railroad ballast, aggregate, etc. so could possibly be found all over the state for those uses.
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Post by 1dave on Sept 28, 2022 10:30:57 GMT -5
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Post by vegasjames on Sept 28, 2022 16:58:42 GMT -5
They are likely quartzite. Banded quartzite is common in several locations around Southern Nevada. I have found a lot of banded purple quartzite out by Pahrump and about 10 miles North of Indian Springs.
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