Another interesting fossil I received from my friend Don were a couple of individual valves from a Pelecypod called Nucula percrassa. The neat thing about them is that the mother of pearl has been preserved for the last 65 +/- million years.
Here you can see the shine of the mother of pearl (or nacre) on the interior of the shell. In daylight there is a faint pink sheen which is not picked up well by my camera.
This shell came from the Coon Creek formation near Blue Springs, Mississippi. The Coon Creek formation is dated to the latest Cretaceous (Maastrichtian stage).