A similar compound is Bone black or Bone char. Hcl is used to purify it. (Mentioned in ncert that's why pointed it out)
Bone char (Latin: carbo animalis) 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 carbon 7–10%. It is primarily used for filtration and decolorization.