Rosemary Posted May 30, 2019 Share Posted May 30, 2019 Is this a lumen cast of a crinoid column? Secondly, is it geodized? Link to comment Share on other sites More sharing options...
ynot Posted May 30, 2019 Share Posted May 30, 2019 Looks like a columnal. By the loosest definition of "geodized" it could be called that. 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...
Rosemary Posted May 30, 2019 Author Share Posted May 30, 2019 I'm confused by what is geodized and what is not. Also, the difference btn geodized and silicified. Link to comment Share on other sites More sharing options...
ynot Posted May 30, 2019 Share Posted May 30, 2019 A geode os a rock with a crust/shell and a crystal lined hollow in it. They should be easily separated from the bedrock they are found in. They can be quartz (silicate), or other minerals. Silicified - replaced by quartz minerals. Has nothing to do with whether it is a geode or not. 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...
Rosemary Posted May 30, 2019 Author Share Posted May 30, 2019 A follow-up question: Are the following examples of geodized and silicified? Link to comment Share on other sites More sharing options...
ynot Posted May 30, 2019 Share Posted May 30, 2019 To tell if they are silicate (quartz) a hardness test is needed. Does it scratch a knife? Again, by the loosest definition of "geodeized", yes they are. The second one looks like it has some "beekite" formation going on. Beekite is a form of silicate (quartz). 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...
Mark Kmiecik Posted May 30, 2019 Share Posted May 30, 2019 Google "geode" and look at the images. Geode refers to a very specific type of rock. Mark. Fossil hunting is easy -- they don't run away when you shoot at them! Link to comment Share on other sites More sharing options...
ynot Posted May 30, 2019 Share Posted May 30, 2019 Your rocks would be more consistent with "midwest sedimentary type geodes" . There are several differing types of "geode". 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...
Rosemary Posted May 30, 2019 Author Share Posted May 30, 2019 Thx for the helpful information everyone. The existence of different types of geodes is likely the source of my confusion. Almost all of my fossils come from one area that was bulldozed, so I'm sifting through tons of upturned dirt. Link to comment Share on other sites More sharing options...
Fossildude19 Posted May 30, 2019 Share Posted May 30, 2019 Rosemary, your first item is indeed a lumen cast. Pretty one, too. 1 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...
Rosemary Posted May 31, 2019 Author Share Posted May 31, 2019 Thank you. :-) Link to comment Share on other sites More sharing options...
Oxytropidoceras Posted May 31, 2019 Share Posted May 31, 2019 Also, in terms of geodes, look up " silicified evaporite syndrome." Some references are given at: http://www.thefossilforum.com/index.php?/topic/66980-crinoid-blossom-found-in-east-central-illinois/&tab=comments#comment-702618 Also, online there is: Milliken, K.L., 1977. Silicified evaporite nodules from the Mississippian rocks of southern Kentucky and northern Tennessee (Doctoral dissertation). https://repositories.lib.utexas.edu/handle/2152/62091 Yours, Paul H. Link to comment Share on other sites More sharing options...
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