Mother-of-pearl
Here is a rare example of mother-of-pearl preserved unchanged for 200 million years. The belemnite shell is composed of many fine layers, so fine in fact that they split the light into rainbow colours, creating the iridescence. The heavy, pointed shell is missing on this specimen but what is also preserved is the phragmocone, the chambered section of the shell that was filled with gas to help the animal float.
