I used to belly dance. You couldn’t pay me to wear a gem in my navel.
Anyway, most dancers try to glue a flat-backed glass stone into their
navel with spirit gum adhesive. It won’t stay. Ask your customer to do a
belly roll for you. When you see the rippling motion of her abdominal
muscles, you’ll understand why you cannot simply fit a gem there. You
cannot expect any stone to stay what amounts to a flexible bezel.
This is what I would suggest. Make a bezel about the size of her
navel. Solder a ring on either side. Use a fine, strong chain (box) to
encircle her waist. Inevitably, this will drop to the lowest point
(hips). A tight chain will break when she dances. Sprit gum might hold
the bezel in place, with chain to prevent loss. Overall, it’s a bad idea.
Allyson (Amalia)Egyptian & Tunisian Dance- now jewelry & gemology