This piece is a head; the central circle is the eye.
A person who has seen something, they know a secret but they are not talking about it.
In Shona society, people do not tend to offer information or opinions unless asked directly. Perhaps they feel they will get the blame for being the messenger! Fear of witchcraft may well be partly involved as well. You wouldn’t want to cast aspersions on someone who might then have reason to do you or your family harm. So best to stay silent, on the whole, and not rock the boat.
‘Cobalt stone’ is the local Zimbabwean name given to a type of serpentine stone that is typically this lovely mixture of purple and green. It comes from the area around the town of Mvurwi in northern Zimbabwe. It does not (as far as we know) contain any cobalt mineral, but may originally have been discovered near a cobalt mine.
The colours in the stone are entirely natural, merely enhanced by the application of a coat of clear wax. Crystals of mica within the stone glitter in the sunlight.