Al-Nawawi : al-Majmu sharh al-Muhadhdhab
(Total Polite Explanation)(d1277)
----------------------------------------------------
Taken from: http://www.islamweb.net/emerath/index.php?page=showfatwa&FatwaId=85298
Our opinion is that the bone (and tusks) of the elephant is impure regardless of whether, it was taken of the elephant after its slaughtering or after a normal death.
Note: Al-Nawawi is the fiqh authority for the Shafi school of jurisprudence