Only want to add some reading stuff.
Here one site from cites:
http://www.cites.org/eng/resources/p...vory-guide.pdf
And here one from U.S. Fish and Wildlife Service:
http://www.lab.fws.gov/ivory_natural.php#hippo
And here one from the International Ivory Society:
http://www.internationalivorysociety...y-bob-weisblut
And there will a booklet coming for ivory identification:
http://dcgia.org/2012/10/14/ivory-id...op-bobby-mann/