Bone charcoal is a unique adsorbent composed principally of carbon and hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ the latter being the inorganic constituent of natural bone. The carbon content of the bone charcoal is derived from the complete carbonization of the naturally occurring organic content of the raw material (bone) and is around 10% by weight of the finished product.

During the manufacturing process, a micro-porous structure of wide pore size distribution is formed within both the carbon and the hydroxyapatite components. Unlike many other charcoals and activated carbons, this porosity is achieved totally by thermal means without the use of any other chemical additives. The process operates at temperatures up to 1000°C and carbonization time is around 12 hours.

Each of the two components of bone charcoal, the carbon and the hydroxyapatite, play a distinct role in the adsorption process. The carbon surface adsorbs weakly anionic molecules while the hydroxyapatite adsorbs strongly charged molecules together with many inorganic ions. The total surface area of bone charcoal is approximately 100 m²/g of which around 50% is attributable to the carbon content. The product also exhibits a unique buffering capacity, thus maintaining alkalinity of the adsorbate.