I bought a large rectangular black stone in the marketplace in Niamey - an onyx or perhaps a black agate. I wondered what to do with it, then hit on the idea of a box, a little place where you could keep something secret. I took it to one of best Tuareg smiths in Agadez, Djabba Hamad. And he produced something beautiful. It was a tough job because the stone wasnt regular, it wasnt a perfect rectangle but we found a solution in the end.