brachiomyback Posted October 24, 2011 Share Posted October 24, 2011 Specimens from an Upper Ordovician Period, Leipers Formation (Maysville Group) that was deposited approximately 445 million years ago in the Nashville, Tennessee area. Among all of the gray limestone of the Leipers Formation, you will find a white rock. This is gypsum (calcium sulfate). Gypsum is an evaporite which forms only under conditions of very high salinity. Some of the gypsum forms nodules in pockets in the sediment. These conditions occur in hot climates, in areas separated from the main sea, where evaporation makes the area very saline. Under these conditions, calcium sulfate becomes supersaturated and crystallizes. Mineralization therefore can occur in hollowed out centers of fossils, such as brachiopods. In many ways, the mineralization of these hollow fossils resembles typical Midwestern geodes. The following are examples of “geodized” brachiopods (Platystrophia ponderosa) that I found. enjoy.... Link to comment Share on other sites More sharing options...
brachiomyback Posted October 24, 2011 Author Share Posted October 24, 2011 Geodized Gastropod Link to comment Share on other sites More sharing options...
JimB88 Posted October 24, 2011 Share Posted October 24, 2011 cool stuff..I found some in the Bigbys as well! Link to comment Share on other sites More sharing options...
Auspex Posted October 24, 2011 Share Posted October 24, 2011 Geology and paleoecology, with a side of very neat fossils! Thanks Brad! "There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant “Try to learn something about everything and everything about something.” - Thomas Henry Huxley >Paleontology is an evolving science. >May your wonders never cease! Link to comment Share on other sites More sharing options...
astron Posted October 24, 2011 Share Posted October 24, 2011 Impressive finds indeed Thanks for showing Astrinos P. Damianakis Link to comment Share on other sites More sharing options...
Shamalama Posted October 25, 2011 Share Posted October 25, 2011 I love the geodeized brachs. Two of my hobbies combined into one specimen! I've never found any in KY, IN or OH with Selenite in them though. -Dave __________________________________________________ Geologists on the whole are inconsistent drivers. When a roadcut presents itself, they tend to lurch and weave. To them, the roadcut is a portal, a fragment of a regional story, a proscenium arch that leads their imaginations into the earth and through the surrounding terrain. - John McPheeIf I'm going to drive safely, I can't do geology. - John McPheeCheck out my Blog for more fossils I've found: http://viewsofthemahantango.blogspot.com/ Link to comment Share on other sites More sharing options...
brachiomyback Posted October 25, 2011 Author Share Posted October 25, 2011 fyi.... Mineralization of Geodized Brachiopods Link to comment Share on other sites More sharing options...
Shamalama Posted October 25, 2011 Share Posted October 25, 2011 That is a nice web page with good information. Thanks for the link! -Dave __________________________________________________ Geologists on the whole are inconsistent drivers. When a roadcut presents itself, they tend to lurch and weave. To them, the roadcut is a portal, a fragment of a regional story, a proscenium arch that leads their imaginations into the earth and through the surrounding terrain. - John McPheeIf I'm going to drive safely, I can't do geology. - John McPheeCheck out my Blog for more fossils I've found: http://viewsofthemahantango.blogspot.com/ Link to comment Share on other sites More sharing options...
Lloyd Posted November 1, 2011 Share Posted November 1, 2011 Good finds. There is a place in Florida where you can find clams with Calcite in them. Link to comment Share on other sites More sharing options...
MikeD Posted November 3, 2011 Share Posted November 3, 2011 I'll have to take a second look at mine (one of these days). I just assumed the ones I have were all calcite. Link to comment Share on other sites More sharing options...
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