CraigHyatt Posted May 24, 2016 Share Posted May 24, 2016 (edited) These finds are from Eagle Pass, TX, Upper Cretaceous, marine, found lying on the ground on a layer of sandstone at a construction site. I see a lot of these doodads, but never picked one up until today when I sat down on a rock for a rest. I noticed it had a bunch of little cubic crystals. I thought maybe iron pyrite, but some of the dark brown crystals almost have an organic look to them, and aren't quite as regular in size and proportion as I'd expect crystals to be. The other thing is most of the objects are roughly the same size, proportions, and have similar rounding. I thought there was a chance they might be coprolites and the bits were chewed up chitin. If they are, then clearly the host wasn't getting enough fiber in its diet. I'll see whether Lori agrees or just poopoos my theory. Edit: You know, the more I look at the magnified images, I think they are just inorganic crystals. Stuff that had been chewed up wouldn't be that regularly shaped. Also, the crystals have that "fractal" self-similar look to them. Not sure why they got clumped together in similar fashion for each specimen though. I probably need to break them open and see what's inside. Edited May 24, 2016 by CraigHyatt 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...
sixgill pete Posted May 24, 2016 Share Posted May 24, 2016 They do not look anything like the coprolites I find. On that premise I do not think they are. Very cool looking whatever they are. I think they are geologic. Bulldozers and dirt Bulldozers and dirt behind the trailer, my desert Them red clay piles are heaven on earth I get my rocks off, bulldozers and dirt Patterson Hood; Drive-By Truckers May 2016 May 2012 Aug 2013, May 2016, Apr 2020 Oct 2022 Link to comment Share on other sites More sharing options...
FossilDudeCO Posted May 24, 2016 Share Posted May 24, 2016 How heavy are these? Link to comment Share on other sites More sharing options...
CraigHyatt Posted May 24, 2016 Author Share Posted May 24, 2016 They do not look anything like the coprolites I find. On that premise I do not think they are. Very cool looking whatever they are. I think they are geologic. Yeah, you are probably right. I broke open all 4 of them. Three of them look like iron concretions. The "yellow" one looks like a conglomerate. 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...
FossilDudeCO Posted May 24, 2016 Share Posted May 24, 2016 I am no expert but I am thinking they look similar to some marcasite I have seen before Link to comment Share on other sites More sharing options...
CraigHyatt Posted May 24, 2016 Author Share Posted May 24, 2016 How heavy are these? This chunk weighs about 15 g (using a stack of pennies to compare). The volume is roughly 8 cm^3 so the density is roughly 2 g/cm^3. 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...
Fossildude19 Posted May 24, 2016 Share Posted May 24, 2016 Definitely geologic in nature. Some form of crystal . 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...
CraigHyatt Posted May 24, 2016 Author Share Posted May 24, 2016 Thanks. The magnified marcasite images I found look pretty similar. Mix of yellow-ish and flat brown crystals. 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...
Al Dente Posted May 24, 2016 Share Posted May 24, 2016 (edited) They could be pyrite pseudomorphs. Edited May 24, 2016 by Al Dente Link to comment Share on other sites More sharing options...
tmaier Posted May 24, 2016 Share Posted May 24, 2016 I second iron sulfide crystals (pyrite). They are cubic, like your photo, and the color is right. https://en.wikipedia.org/wiki/Pyrite I don't know anything about poop, but I understand every does. =-) I had a computer crash, and now I'm stuck with no editor features again! =-( Link to comment Share on other sites More sharing options...
Darktooth Posted May 24, 2016 Share Posted May 24, 2016 I agree that they are some sort of mineral. However they are still a very interesting find. I like Trilo-butts and I cannot lie. Link to comment Share on other sites More sharing options...
GeschWhat Posted May 24, 2016 Share Posted May 24, 2016 It is almost impossible to tell if little pyritized nuggets like these are coprolites unless you can see bone/scale inclusions. If it is any consolation, in a sense they were probably formed by the waste of sulfate-reducing (anaerobic) bacteria. If it had fecal origins it could have happened something like this: The poo (or other decaying organic matter) floats to the bottom of the sea and is covered in iron-rich sediment (or there is a heavy iron content in the water). It is not exposed to oxygen, so it doesn't decompose in a traditional sense. However, the poo contains sulfates (the stinky stuff) on which sulfate-reducing bacteria thrive. The bacteria takes in sulfates and produces sulfide waste (aka anaerobic respiration) which combines with the iron. After thousands/millions of years, voila: poo-l's gold (iron pyrite). Did yours start out as fecal matter? Only Mother Nature knows for sure! 1 Lori www.areallycrappystory.com/fossils www.facebook.com/fossilpoo Link to comment Share on other sites More sharing options...
CraigHyatt Posted May 24, 2016 Author Share Posted May 24, 2016 Thanks all! 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...
DPS Ammonite Posted May 24, 2016 Share Posted May 24, 2016 Pseudomorphs of pyrite are common. Pyrite is unstable and reacts with water and air (rusts) to form different minerals. Al Dente is correct... your pyrite is changing into other iron bearing minerals such as limonite, hematite and possibly maghemite which is magnetic. Are the pyrite pseudomorphs magnetic? For pictures of pyrite pseudomorphs see Mindat: http://www.mindat.org/mesg-82-202977.html 1 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 May 24, 2016 Author Share Posted May 24, 2016 (edited) Pseudomorphs of pyrite are common. Pyrite is unstable and reacts with water and air (rusts) to form different minerals. Al Dente is correct... your pyrite is changing into other iron bearing minerals such as limonite, hematite and possibly maghemite which is magnetic. Are the pyrite pseudomorphs magnetic? For pictures of pyrite pseudomorphs see Mindat: http://www.mindat.org/mesg-82-202977.html Dang. Left my magnet in my other pants. ;-)Edit: very handy link, going in my bookmarks! Edited May 24, 2016 by CraigHyatt 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...
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