A friend of mine lost one of the little triangle stones in her wedding ring. To repair it, I used the jewelers saw to cut a triangle from a slice of stabilized turquoise. I used sandpaper to fit it. In order to handle it, I glued the stone on a wooden stick. When the stone fit snug inside the channel, I glued the stone in. In a few hours, I will cut off the stick, then grind the end of the stick flush with the stone. This is the first repair like this that I have ever attempted, and the solution came to me through dreaming about it. I will post the results as soon as I am sure the stone is secure.