I recently got an "enhanced grab bag" of fossil matrix. The matrix is from NC, the enhanced portion is shark teeth added in from SC & FL. This large chunk of something was in with it. At first I thought a nice big bone piece, after cleaning it up, not sure if it's bone or some sort of mineral deposit. Pics 1 $ 2 are of the sides, 3 is the narrow "top" & 4 is the split bottom section. The remaining pics will follow. It was just under 17 cm long until I cut about 2 cm or so off the narrow end, 3.5 cm wide & 4.5 cm thick. In the split section & 1 end there are several small crystals embedded in the openings. Red, green, yellow, clear. I can take pics of some of them if needed.