Black Marble Petrosphere (Prototype)

There are over 500 recorded examples of petrospheres, or carved stone balls from the neolithic period. Most have been found in Scotland.
There are lots of theories about their original purpose. I prefer to just enjoy them as fabulous objects and I've been fortunate enough to handle several of them.
This is my take on them. It isn't based on a particular example but it is a typical size at about 7cm across.
 
This is a prototype so it's a little rough. But, so are the originals!