oh, yeah, there's lots of ways you can do bone.
The easy way is to use an ivory-colored clay, maybe white mixed with a little beige and a little yellow, maybe even a little translucent (I find it tends to make faux natural materials look more realistic) and then "antique" the cured piece by painting on brown acrylic paint and wiping it off before it dries, leaving "dirt" in the crevices/carvings (like this http://www.sculpey.com/Projects/projects_AsianBeadBracelet.htm
The more complicated way is to make one of the many faux ivory/bone recipes you can find on the internet or one of the zillions of PC-related books (the recipes in Victoria Hughes "Polymer: the Chameleon Clay" and in Sue Heaser's "techniques" book, the actual name of which currently escapes me, are the ones I think are best).
ETA: AHA! Here's a good link to the way I do ivory/bone: http://www.thepolyparrot.com/faux_looks.pdf