doushantuo Posted July 20, 2016 Share Posted July 20, 2016 mineralogically,quite a few possibilities exist: ferroan and non-ferroan calcite,silica(rare),dolomite,and of course,the famous pyrite,low Mg calcite... Link to comment Share on other sites More sharing options...
ynot Posted July 20, 2016 Share Posted July 20, 2016 Dumb question: I have found a few specimens with part of the aragonitic shell present, but most are just casts as the specimen shown below. I wonder if it's possible to find the *cast* of an ammonite that created a track, even with the aragonite dissolved away? That is a different question than the one I answered above. (this is confusing!) The piece that made the track could have traveled for 100's of yards or a few miles. The chances of finding it are slim to none. Tony PS I noticed that the original post has changed also, now all the subsequent conversation makes no sense. Darwin said: " Man sprang from monkeys." Will Rogers said: " Some of them didn't spring far enough." My Fossil collection - My Mineral collection My favorite thread on TFF. Link to comment Share on other sites More sharing options...
doushantuo Posted July 20, 2016 Share Posted July 20, 2016 Which is a reminder to everyone:if you ever find trackmaker and track together:that's PRICELESS Link to comment Share on other sites More sharing options...
DPS Ammonite Posted July 20, 2016 Share Posted July 20, 2016 Dumb question: I have found a few specimens with part of the aragonitic shell present, but most are just casts as the specimen shown below. I wonder if it's possible to find the *cast* of an ammonite that created a track, even with the aragonite dissolved away? image.jpeg I guess it's a moot point because if it left the track while still in the ocean, then the shell would still be in its original form. How do you know you have seen specimens with aragonite? Ammonites have an internal nacreous layer of aragonite. The nacreous layer in ammonites and other mullusks is sometimes preserved in shales in the Eagleford Group and ironstones in the Weno and Paw Paw Formations in Texas. Your specimen is an internal mold and not a cast since a mold (sediment filling) is pressed against the original (now dissolved) shell. You can find casts of ammonites in Texas; finding the one that made the track... very unlikely. My goal is to leave no stone or fossil unturned. See my Arizona Paleontology Guide link The best single resource for Arizona paleontology anywhere. Link to comment Share on other sites More sharing options...
CraigHyatt Posted July 20, 2016 Author Share Posted July 20, 2016 That is a different question than the one I answered above. (this is confusing!) The piece that made the track could have traveled for 100's of yards or a few miles. The chances of finding it are slim to none. Tony PS I noticed that the original post has changed also, now all the subsequent conversation makes no sense. Sorry about that. I realized the original post didn't capture my real question. It might be confusing for everybody else, but at least *I* understand the thread. Thanks. :-) Info: Craig Hyatt, retired software/electrical engineer Experience: Beginner, fossil hunting less than a year Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert Formation: Escondido, Marine, Upper Cretaceous Materials: Sandstone, Mudstone, Shale, Chert, Chalk Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus Reference: http://txfossils.com/Txfossils.html Link to comment Share on other sites More sharing options...
CraigHyatt Posted July 20, 2016 Author Share Posted July 20, 2016 How do you know you have seen specimens with aragonite? Ammonites have an internal nacreous layer of aragonite. The nacreous layer in ammonites and other mullusks is sometimes preserved in shales in the Eagleford Group and ironstones in the Weno and Paw Paw Formations in Texas. Your specimen is an internal mold and not a cast since a mold (sediment filling) is pressed against the original (now dissolved) shell. You can find casts of ammonites in Texas. I should say I *think* they still had some of the shiny reddish-brown shell. The one pictured above definitely looks like a cast. Let me look through my old posts to see if I can find one with the "shell".Edit: Like this. Any of the original shell left or just colored by minerals. I remember it being pretty smooth and shiny. http://www.thefossilforum.com/index.php?/topic/65199-south-texas-upper-cretaceous-ammonite/ Info: Craig Hyatt, retired software/electrical engineer Experience: Beginner, fossil hunting less than a year Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert Formation: Escondido, Marine, Upper Cretaceous Materials: Sandstone, Mudstone, Shale, Chert, Chalk Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus Reference: http://txfossils.com/Txfossils.html Link to comment Share on other sites More sharing options...
ynot Posted July 20, 2016 Share Posted July 20, 2016 Without doing a chemical analyses of the material there is no way to be sure. Tony Darwin said: " Man sprang from monkeys." Will Rogers said: " Some of them didn't spring far enough." My Fossil collection - My Mineral collection My favorite thread on TFF. Link to comment Share on other sites More sharing options...
CraigHyatt Posted July 20, 2016 Author Share Posted July 20, 2016 Without doing a chemical analyses of the material there is no way to be sure. Tony I guess it would fizz in HCl if some type of carbonate. As I recall the "shell" really looked like you could chip it off of the inner mold. Next time I find one, I'll test it. Unfortunately, I give away most of what I find to kids. I should start keeping some reference samples. Info: Craig Hyatt, retired software/electrical engineer Experience: Beginner, fossil hunting less than a year Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert Formation: Escondido, Marine, Upper Cretaceous Materials: Sandstone, Mudstone, Shale, Chert, Chalk Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus Reference: http://txfossils.com/Txfossils.html Link to comment Share on other sites More sharing options...
doushantuo Posted July 20, 2016 Share Posted July 20, 2016 I guess it would fizz in HCl if some type of carbonate. As I recall the "shell" really looked like you could chip it off of the inner mold. Next time I find one, I'll test it. Unfortunately, I give away most of what I find to kids. I should start keeping some reference samples. suddenly,I feel fourteen again Link to comment Share on other sites More sharing options...
ynot Posted July 20, 2016 Share Posted July 20, 2016 Any calcite mineral will fizz to some degree. An acid fizz test would not tell if it was the original shell or a calcite replacement. Remember that the shell was replaced by whatever mineral while buried, and whatever mineral replaced it retained the shape and thickness of the original shell. Tony Darwin said: " Man sprang from monkeys." Will Rogers said: " Some of them didn't spring far enough." My Fossil collection - My Mineral collection My favorite thread on TFF. Link to comment Share on other sites More sharing options...
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