ericabelle
spending too much on rocks
Instagram acct: @erica_shoots_everything
Member since April 2021
Posts: 482
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Post by ericabelle on Jun 3, 2021 7:47:42 GMT -5
So, I found this rock on the banks of a creek in Mammoth Spring, Arkansas; and I'm baffled by the strange breaking points. I also found two other much smaller rocks like it, and they have one or two square broken areas like this. The rock seems to have some translucency on the edges, but you cannot see light through the middle. Stainless steel doesn't scratch it. it has many white dots of material throughout, more apparent when wet. Maybe it's something common like chert or quartzite, but I hadn't seen breakage like this, so I thought I'd see what everyone thought about it. Here it is dry: Here it is wet - you can see many white dots more clearly And here is the back, with a little crystal pocket at the top:
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Post by mohs on Jun 3, 2021 11:02:10 GMT -5
pointing out the rocks spots is interesting sure I've seen that type of rock before
but now ya got me thinking how do those spots form? baffling
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lookatthat
Cave Dweller
Whatever there is to be found.
Member since May 2017
Posts: 1,360
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Post by lookatthat on Jun 3, 2021 11:05:52 GMT -5
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lookatthat
Cave Dweller
Whatever there is to be found.
Member since May 2017
Posts: 1,360
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Post by lookatthat on Jun 3, 2021 11:16:38 GMT -5
Oh, that's funny... I posted a row of question marks, I had no idea they'd come out with that face instead!
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ericabelle
spending too much on rocks
Instagram acct: @erica_shoots_everything
Member since April 2021
Posts: 482
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Post by ericabelle on Jun 3, 2021 11:32:14 GMT -5
@mohs and lookatthat , baffling is certainly the word for it! Haha- a row of question marks turns into a row of frowning faces? What other secret codes are there to discover?😮
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Post by Rockoonz on Jun 3, 2021 19:28:38 GMT -5
Dots certainly interesting. The edge shows conchoidal where it has broken, so definitely primarily silica, and translucency makes me think agate. The line of squares is the shock pattern you hate to see when knapping, think they call it a shelf, nasty bugger to correct, came from something striking the rock way back when. One theory on polkadots in metamorphic rock is that the agate, or whatever, formed around and partially replaced tiny concretions that had formed around grains of sand. Hard to say, I'm getting pretty old but I wasn't there when it happened.
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Post by fernwood on Jun 4, 2021 2:48:53 GMT -5
Check out Oolictic agates or Oolites.
Oolitic Agates have egg like round inclusions. Often called "Egg Stones." Deep in the water of ancient seas, small grains of sand and debris were rocked back and forth along the sea floor, picking up concentric coats of deposition like the building up of a pearl.
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tumblee
starting to spend too much on rocks
Member since March 2021
Posts: 154
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Post by tumblee on Jun 4, 2021 3:56:53 GMT -5
Whatever it is, looks like it had been turned ~90 degrees a long long time ago.
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ericabelle
spending too much on rocks
Instagram acct: @erica_shoots_everything
Member since April 2021
Posts: 482
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Post by ericabelle on Jun 4, 2021 7:14:42 GMT -5
Dots certainly interesting. The edge shows conchoidal where it has broken, so definitely primarily silica, and translucency makes me think agate. The line of squares is the shock pattern you hate to see when knapping, think they call it a shelf, nasty bugger to correct, came from something striking the rock way back when. One theory on polkadots in metamorphic rock is that the agate, or whatever, formed around and partially replaced tiny concretions that had formed around grains of sand. Hard to say, I'm getting pretty old but I wasn't there when it happened. That is so interesting - the shock pattern and the "sand agate"! Thanks so much for your info - I find some interesting things at that creek!
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ericabelle
spending too much on rocks
Instagram acct: @erica_shoots_everything
Member since April 2021
Posts: 482
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Post by ericabelle on Jun 4, 2021 7:19:34 GMT -5
Check out Oolictic agates or Oolites. Oolitic Agates have egg like round inclusions. Often called "Egg Stones." Deep in the water of ancient seas, small grains of sand and debris were rocked back and forth along the sea floor, picking up concentric coats of deposition like the building up of a pearl. Wow! I bet this would be interesting under magnification - thanks for the info!
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Post by fernwood on Jun 4, 2021 7:27:41 GMT -5
Rocks with Oolites are common on my WI property. Yes, photos are amazing when macro or magnified.
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Post by rmf on Jun 4, 2021 8:54:50 GMT -5
This has no cleavage. This does have a sub conchoidal fracture. This is oolitic chert. I have pickup up some in your fair state. This will take a great polish.
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mjflinty
spending too much on rocks
Member since September 2011
Posts: 356
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Post by mjflinty on Jun 5, 2021 6:51:01 GMT -5
You found oolitic chert. The fracture is conchoidal and the squareish spots are fairly common on cherts as they weather and break apart naturally.
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ericabelle
spending too much on rocks
Instagram acct: @erica_shoots_everything
Member since April 2021
Posts: 482
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Post by ericabelle on Jun 6, 2021 13:25:12 GMT -5
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Post by Peruano on Jun 6, 2021 14:40:22 GMT -5
Score one for reading; and one for applying the info in your backyard environment.
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oldschoolrocker
fully equipped rock polisher
Member since January 2019
Posts: 1,540
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Post by oldschoolrocker on Jun 6, 2021 14:41:48 GMT -5
Now let's see the innards of that 2nd one!
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Brian
fully equipped rock polisher
Member since July 2020
Posts: 1,506
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Post by Brian on Jun 6, 2021 18:26:10 GMT -5
That backyard find is really cool!
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Post by jasoninsd on Jun 6, 2021 20:35:12 GMT -5
ericabelle - That oolite find in your backyard is amazing! I love the looks of that piece!
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ericabelle
spending too much on rocks
Instagram acct: @erica_shoots_everything
Member since April 2021
Posts: 482
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Post by ericabelle on Jun 7, 2021 6:58:24 GMT -5
Now let's see the innards of that 2nd one! Oh no! I don't know if I can cut it - I may see if I can hand polish just the smooth area so that I can leave the textured part as-is.
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ericabelle
spending too much on rocks
Instagram acct: @erica_shoots_everything
Member since April 2021
Posts: 482
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Post by ericabelle on Jun 7, 2021 6:58:53 GMT -5
That backyard find is really cool! Thanks, Brian!
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