Bone ash

Bone ash is a white material produced by calcining animal bones, heating them to a high temperature, typically around one thousand degrees Celsius, to burn away all organic matter and leave behind the mineral content, a process that leaves most bones with their original cellular structure intact. The resulting material is composed mostly of calcium oxide and phosphorus pentoxide, with a melting point near 1670 degrees Celsius, and commercially it makes up roughly half the formula of bone china and reacts with the other ingredients during firing. Bone ash also serves as an organic fertilizer on its own or after treatment with sulfuric acid to make superphosphate, a more water soluble fertilizer, and its porous structure and high melting point make it useful in metallurgy for the cupellation process that refines precious metals such as gold and silver, and in foundries as a release agent and thermal barrier. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/