Charcoal is an amorphous allotrope of carbon, meaning it's a form of carbon that exists in an irregular, non-crystalline structure.

• Wood charcoal has a porous structure that provides a large surface area for adsorption, allowing it to absorb coloured material from sugar .

• Animal charcoal is obtained from bones, blood, and horn through destructive distillation, it has good adsorptive power and can decolourize raw sugar when boiled together. 

• Activated carbon plays a multifaceted role in sugar cane refining, removing impurities and colourants from sugar solutions. Therefore, Charcoal is the allotrope of carbon used in the decolourization of sugar.