What is "bone char"

n. black substance containing char in the form of carbonized bone; used as a black pigment [syn: bone black, animal black, animal charcoal]

Bone char is a porous, black, granular material produced by charring animal bones. Its composition varies depending on how it is made; however, it consists mainly of tricalcium phosphate (or hydroxylapatite) 57–80%, calcium carbonate 6–10% and activated carbon 7–10%. It is primarily used for filtration and decolorization.