Shark teeth that change color..  Here is one... a Mako. A Photo taken within 10 minutes of removing from a heavy blanket of mud, gravel, clay mixture.  This tooth had not seen daylight in a couple of million years. Then a photo of the same tooth 2 hours later when I arrived home.  Yes I applied water, then oil and neither the  blade or especially the root darkens again..   If some type of organism that dies/fade in sun light, how about this hemi that came from the exact same