Onychaster Starfish Fossil

Onychaster sp. starfish fossil that crawled the seafloor in the Mississippian Period. This fossil is on display on the first floor of the Indiana State Museum as of May 2012. More than likely this fossil is from Crawfordsville, Indiana. That is a some beautiful 3-D prep work!

Learn more about the Indiana State Museum at their web site.

Calcium Acetate or the Lemon Meringue Pie Effect

A while back I was working with some North Evans Limestone samples looking for conodont fossils. Dave at Views of the Mahantango blog had left me with some specimens to work with. He told me to dissolve the pieces in vinegar and then look for small fossils.  This worked (see pictures at bottom of post) and afterwards I left the samples in the sun room where I do most of my photography and microscope work.

Several weeks passed when I noticed something interesting in the container, formations of white crystals were forming. As it turns out a chemical reaction was taking place, one in which the limestone samples (calcium carbonate) were interacting with the vinegar (acetic acid) to form water, carbon dioxide, and calcium acetate (calcium salt). The carbon dioxide floated off into the atmosphere, the water eventually evaporated, which just left the limestone and crystallized calcium acetate.

Limestone + Vinegar =  Calcium Salt + Water + Carbon Dioxide

CaCO₃ + 2CH₃COOH = Ca(CH₃COO)₂ + H₂O + CO₂

The calcium acetate formed a texture and color that reminded me of the layer of meringue that one finds on lemon pies.

Lemon Meringue Pie - photo by Renee Comet (1994) - wikipedia.org

The last three pictures are of some Devonian Period conodont fossils I found in the limestone. Not sure of their names but if I had to guess maybe a Prioniodus sp. Learn more at the web site of North Evans Limestone fossils found at Penn-Dixie Cement Quarry in Hamburg, New York.

Silurian Green Fossil - Bickmorites?

Sometimes when one is searching for fossils in the field, color is important as opposed to just trying to visually match shapes and patterns. In the case of today's posting, the color green is important. The Silurian Period Louisville Limestone found in Jefferson County, Kentucky at times has green blotches that show through. I assume this is a sign of some sort of copper being present. (UPDATE: see comment section as the green material might be glauconite.) My cousin told me this could be a sign of a cephalopod fossil which tend to be difficult to find in this rock layer. Mostly one finds corals (chain or colonial types) and some brachiopods with rare trilobite or graptolite fragments. Years ago, I saw cephalopod fossils found by others but recently I came across the remains shown in these first three pictures. After visiting the Indiana State Museum and seeing some of their Silurian cephalopod specimens, a green color was present in some of those specimens. Their material was from the Wabash Formation if I remember correctly. This formation might not quite match up with the Louisville Limestone.

These next two Bickmorites sp. specimens can be found on the first floor of the Indiana State Museum as of May 2012. They are in the fossil area in the Silurian case.

See a Bickmorites sp. specimen at the Indiana State Museum on-line database.

Last two images are magnified areas of the green fossil I found in the Louisville Limestone. Learn more about these creatures at this web site.

UPDATE:
A reader of this blog, avid fossil collector, and chemist Jack Kesling of Pennsylvania sent me a nice fossil find that relates to this posting. He found this unidentified Silurian cephalopod fossil with a lot of greenish material on it. The fossil was found in the Bertie Formation of Herkimer County, New York.

Photo by Jack Kesling