text: Bone ash is a material often used in cupellation, a process by which precious metals (such as gold and silver) are removed from base metals.
  In cupellation, base metals in an impure sample are oxidized with the help of lead and are vaporized and absorbed into a porous cupellation material, typically made of magnesium or calcium. This leaves the precious metals which do not oxidize behind. Bone ash's extremely porous and calcareous structure as well as its high melting point makes it an ideal candidate for cupellation.