This is a n'anga, a person who speaks with the spirits. People consult them if they have problems, and the n'anga consults with the spirits (usually the ancestors) and comes back with an answer.
He is holding a fly whisk, which is one of the traditional accoutrements of a witchdoctor. The fly whisk is made from horse tail hair, and is used in healing ceremonies. If a person is possessed by bad spirits, the n'anga dips the fly whisk into a concoction and flicks the liquid onto them to drive the spirits away.
This wonderful red and silvery-grey stone is a rediscovered variety of serpentine stone. All the colouration in the stone is entirely natural.