Activated Charcoal is used in soap to create a wonderful pure dark black soap. It is non-staining and will not ruin your washcloths.
It is commonly used in facial soaps.
Common charcoal is manufactured out of coal, peat, wood, petroleum or even coconut shells. “Activated charcoal” is made by manufacturers heating common charcoal in the presence of a gas that causes the charcoal to develop internal spaces or pores that allow activated charcoal to trap chemicals. It is for this reason that activated charcoal is often used to absorb toxic substances.