rockhoundoz
starting to spend too much on rocks
Member since March 2017
Posts: 131
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Post by rockhoundoz on Nov 2, 2018 11:34:46 GMT -5
Found this rock yesterday & my 1st thought was that I had finally found a piece of the infamous Kentucky purple chert. I've long heard about a purple chert material coming from Kentucky, said to knap very well, and have never even seen a piece in person let alone found one. Seen plenty of maroon, pink, red etc.. So I was very happy just to find this as chert, but then after I cleaned it up, noticed it has a clear 'cellular structure' pattern. I believe it to be fossilized something. Maybe 'oolite' as I've learned about from yall on this here website, or other bryozoan/simple marine creature, but one can always hope, heh. Anybody have a possible ID? Thanks! It's about 6 inches long, weighs about 3 pounds, & was found in quaternary alluvial gravel, sitting right on the surface, karst/cave geology all around. Few pics of the shape & surface texture: Some pictures to show the 'cellular structure' I mentioned: This next picture is much closer to the middle/core of the rock, shows a texture that looks pretty different than the parts closer to the surface (dry & wet): The purple is so much more beautiful & intense than I can capture in these low grade photos, 😅.
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Post by MsAli on Nov 2, 2018 12:06:53 GMT -5
Have a way to take a slab off it?
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Post by rockjunquie on Nov 2, 2018 12:12:20 GMT -5
I can't help with ID, but I have to say- You got a sweet looking rock there!
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rockhoundoz
starting to spend too much on rocks
Member since March 2017
Posts: 131
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Post by rockhoundoz on Nov 2, 2018 12:42:14 GMT -5
Have a way to take a slab off it? Yes, it's just a bit intimidating to think about cutting it at the moment.. If someone assures me that it's not dinosaur bone, then I'll feel a lot more comfortable slicing it up ; ). It's also a tricky one to figure out for orienting the cuts because of the heavy fractures, which I'm leaning towards thinking are unhealed so far. Very open for any thoughts/advice on the lapidary side though!
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rockhoundoz
starting to spend too much on rocks
Member since March 2017
Posts: 131
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Post by rockhoundoz on Nov 2, 2018 12:44:53 GMT -5
I can't help with ID, but I have to say- You got a sweet looking rock there! Thanks! Not to sound too weird, but I was so excited about finding it that I stayed up until 3 am, haha..
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Post by rockjunquie on Nov 2, 2018 12:50:33 GMT -5
I can't help with ID, but I have to say- You got a sweet looking rock there! Thanks! Not to sound too weird, but I was so excited about finding it that I stayed up until 3 am, haha.. Yeah, I'd be pretty excited too!
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Post by Peruano on Nov 2, 2018 13:15:20 GMT -5
First off, cherts can have fossils in them since they often form in sedimentary layers. Think of that chert as a silica version of your limestone, it just formed in a different way. Perhaps the white rind on the outside of your specimen will fizz and bubble away with a bit of acid, but if its chert the main purple core will be unaffected. Can you chip off a bit of a window with a small hammer? A conchoidal fracture would be informative and give you an interior look. If you decide to disassemble it, consider making a major cut along, not across a fracture. Just do what you have to do to satisfy your desire to understand the rock. Its your rock and you can do anything or nothing to it in your deliberations.
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Post by MsAli on Nov 2, 2018 13:22:35 GMT -5
Have a way to take a slab off it? Yes, it's just a bit intimidating to think about cutting it at the moment.. If someone assures me that it's not dinosaur bone, then I'll feel a lot more comfortable slicing it up ; ). It's also a tricky one to figure out for orienting the cuts because of the heavy fractures, which I'm leaning towards thinking are unhealed so far. Very open for any thoughts/advice on the lapidary side though! I would cut it along one of those fractures and see what it looks like. Might help you identify it a little better That is just me
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goatgrinder
spending too much on rocks
Make mine a man cave
Member since January 2017
Posts: 368
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Post by goatgrinder on Nov 2, 2018 13:24:59 GMT -5
It really does not look like dino bone. It looks like plain old (structurally) colorful chert. A nice find.
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Post by pauls on Nov 2, 2018 13:56:56 GMT -5
My thought was Flint, but Chert will do just as well, they tend to grade into each other anyway.
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Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Nov 2, 2018 14:30:06 GMT -5
I would do a Mohs hardness test. I also like the idea of taking a cut along a fracture, then flaking off an edge to determine whether it has a conchoidal fracture. Also, is it transparent, translucent or completely opaque? It does look like it has some structure to it, but not organized enough for bone, and the photos aren't clear enough to me to say whether it might be fossil coral (there are some things that look coral-like, but try to get a macro shot close up to one of the "cells").
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rockhoundoz
starting to spend too much on rocks
Member since March 2017
Posts: 131
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Post by rockhoundoz on Nov 2, 2018 16:18:47 GMT -5
Thanks all! I put it in the saw, took off a small end cut & like yall said, became clear that it's purple chert. We have a ton of oolite out here, various sea creatures mixed into the chert, as you noted Peruano, & also a ton of coral 'head' fossils. These coral heads are what most ky agates are replacing, & this purple guy has that general shape & form. Also, lost the nice overcast daylight here & this round of photos suffered in terms of focus and color, heh.. Then, after taking 1 slab off the end, seemed like the fractures (going in many directions throughout the rock) were at least somewhat healed, so I decided to reposition it & cut along the bigger face. In particular, aiming to target the more colorful & 'patterned' skin/rind. It's in between the 6-7 hardness. Softer than ky agate but also it's not the softest chert around. It flakes away quite nicely too. Fracture is conchoidal, but preserves that cell pattern which is throughout the rock (can't remember ever seeing a similar cell pattern after cutting 100's or a thousand pieces of local chert, fossils, coral etc over the last 10 years back home in KY). The cell shape is hard to see in my poor pics, but if ya saw it in person it's all throughout the rock. Highly translucent. Regarding fossil bone, I once read from the University of KY geology dept. that the most common question they receive from the public is not just whether some given rock is a dinosaur bone, but what type of dinosaur 😅. Of course it's basically never dino bone. Fortunately a little wishful thinking never hurt! Also, this chert was found just a stones throw (relatively) from a location where many complete fossil dinosaur skeletons were once found, in the same geologic & physiological setting, so I'll keep hoping to find some one day!
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Post by MsAli on Nov 2, 2018 16:26:43 GMT -5
It is VERY pretty! I cannot wait to see what you do with it
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Post by rockjunquie on Nov 2, 2018 16:39:52 GMT -5
That first picture really says it all- very nice. I hope you cab some of it and show us the pictures.
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Post by fernwood on Nov 2, 2018 16:51:48 GMT -5
I see the oolites. Where I live there is a lot of oolite replacement in coral. That is a very nice rock, whatever it is.
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NRG
fully equipped rock polisher
Member since February 2018
Posts: 1,630
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Post by NRG on Nov 3, 2018 16:46:07 GMT -5
Fluorite is soft and scratches with a pocket knife blade. Does this stone scratch with a pocket knife blade? (Kentucky has fluorite deposits) ETA and I see a cube in one of the original pictures. ETA x2 Bottom right side looks like a cube to me.
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Post by adam on Nov 3, 2018 20:29:32 GMT -5
Nice chert nodule. I've found stuff just like that before, but never in violet. Mostly dull colors. The nodules are pretty common round here. We also get the Kentucky agate.
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Post by adam on Nov 3, 2018 20:30:51 GMT -5
Fluorite is soft and scratches with a pocket knife blade. Does this stone scratch with a pocket knife blade? (Kentucky has fluorite deposits) ETA and I see a cube in one of the original pictures. ETA x2 Bottom right side looks like a cube to me. Chert… definitely. Fluorite is a more western Kentucky occurrence than central and eastern Kentucky.
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rockhoundoz
starting to spend too much on rocks
Member since March 2017
Posts: 131
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Post by rockhoundoz on Nov 5, 2018 13:59:47 GMT -5
Fluorite is soft and scratches with a pocket knife blade. Does this stone scratch with a pocket knife blade? (Kentucky has fluorite deposits) ETA and I see a cube in one of the original pictures. ETA x2 Bottom right side looks like a cube to me. That would be amazing to find a big chunk of purple fluorite out here! adam, rare but possible because there was a nearby mine that produced fluorite some time ago, in central KY. If I recall correctly, there was also even fluorite found near Georgetown KY. Apparently, fluorite is also possible inside geodes from many ky locales. Probably easy to overlook or mistake fluorite for the waaay more common calcite in geodes & agates. This piece though is certainly chalcedony, basically ancient inland sea fossilized chert, but with somewhat agatized areas in the 'rind' & perhaps oolites too. I will post the results of working this stuff : ), have a small carving in mind if I can get a nice piece fracture-free!
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Fossilman
Cave Dweller
Member since January 2009
Posts: 20,681
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Post by Fossilman on Nov 6, 2018 10:51:16 GMT -5
Kind of looks like its from the Oolite family....Nice color...
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