Mahnmut Posted January 1, 2022 Share Posted January 1, 2022 Hello together, I got this one as a gift, all the info I have is "rock with a nice pattern from the Sahara desert ". I am relatively sure its not a fossil, even more so after looking at the macro-fotos. Still it reminded me of tentaculites, and I wonder if there are fossils disguised by desert varnish, or if it is all pure geology. What do you think? Scale is metric, as you can tell by the ten/five small marks to a big one. Best regards, J Try to learn something about everything and everything about something Thomas Henry Huxley Link to comment Share on other sites More sharing options...
Fossildude19 Posted January 1, 2022 Share Posted January 1, 2022 I think this is geologic in nature, but I don't know what would cause this. Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
TqB Posted January 1, 2022 Share Posted January 1, 2022 It looks like cone-in-cone structure. 1 3 Tarquin Link to comment Share on other sites More sharing options...
TyrannosaurusRex Posted January 1, 2022 Share Posted January 1, 2022 Could this be a ventifact? I have a similar piece that’s a ventifact from the Kalahari desert and it bears a very similar resemblance in patterning. Interesting piece, I’m curious what others with more experience will say. Link to comment Share on other sites More sharing options...
Mahnmut Posted January 1, 2022 Author Share Posted January 1, 2022 (edited) 48 minutes ago, TqB said: It looks like cone-in-cone structure. I had to look that one up, Interesting. Wiki tells me that cone-in-cone structures where at first considered fossils ("Cophinus dubius") in the 19th century. Thanks to all your replies. I have seen desert varnish enhancing underlying structures, so cone-in-cone under a layer of varnish seems like a good tentative ID. They do occur in Morocco and Algeria. @TyrannosaurusRex,Wind definitely had its part in the shaping of this rock, so it is a ventifact. below is an example for cone-in-cone from a popular auction site that I would now like to buy if overseas shipping wasnt more than the bid. It really resembles my desert stone a lot, so I consider this enigma solved. Thanks again, J Edited January 1, 2022 by Mahnmut additional info 1 Try to learn something about everything and everything about something Thomas Henry Huxley Link to comment Share on other sites More sharing options...
marguy Posted January 1, 2022 Share Posted January 1, 2022 Hello, it is indeed a form of wind erosion on a rock placed on the ground. Here is a sample that I collected around 1980 near the sand dunes south of Erfoud (Morocco), in side view with these characteristic figures and seen on the underside where it was placed. 2 1 Link to comment Share on other sites More sharing options...
Mahnmut Posted January 1, 2022 Author Share Posted January 1, 2022 Ok, thats an ID in the strict sense that it appears to be identical to your sample. I still wonder if the structure that the wind brought out was cone-in cone, but thats not a fossil question any more. Nice rock! 1 Try to learn something about everything and everything about something Thomas Henry Huxley Link to comment Share on other sites More sharing options...
marguy Posted January 1, 2022 Share Posted January 1, 2022 Hello, @Mahnmut thank you for reactivating my curiosity on the subject; I just found this : https://www.semanticscholar.org/paper/Silicified-Cone-in-Cone-Structures-from-Erfoud-A-Lugli-Reimold/0dab2f78b02cfa6225be887eb05939ac069de1ce (only abstract) .... which answers our question and article: https://www.univie.ac.at/geochemistry/koeberl/publikation_list/263-Shatter cones-Impact Tectonics-2005.pdf I wish you a good reading . 1 Link to comment Share on other sites More sharing options...
abyssunder Posted January 1, 2022 Share Posted January 1, 2022 If my mind reacts it correctly, it was "maybe" a topic on TFF with something similar, I can't remember, but the OP gave the exact ID. " We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. " Thomas Mann My Library Link to comment Share on other sites More sharing options...
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