Dha

[Mark]

One way to tell ivory from bone and antler is to shine an ultra-violet light on it. Ivory will glow a very bright quite, while anter and bone will only a weak fluorescense (plastice none at all, BTW). It is harder to distiguish under a dark patination, though, and such things as "bright" and "weak" are relative terms that are hard to quantify with known reference standards.