Cleaning Ostrich Shell beads...Ideas?

Q: I picked up some ostrich shell beads, but they have some sort of tacky black crud on them. Does anyone: 1 - Know what it is? 2 - Have ideas on removing it? Since I can test a cleaning method on a single bead, it should be pretty safe. I just want to avoid having to scrub each bead with a toothbrush. I have a sonicator, but am assuming that it will only weaken the beads.

A: I had a few strands and assumed that it was a result of having been worn for an unknown number of years by an unknown number of human beings. The strands were obviously not newly made. Soap (detergent) and water cleaned them up okay, but to get them totally clean means you probably have to take the strand apart and clean each disk, which is a lot of work. I think I may have given some of them a bath in the ultrasonic cleaner. Go ahead and test one bead and see what happens. It will probably be okay. Try a solution of four parts water to one part vinegar, for no more than 24 hours. This will soften the surface calcium, and should enable cleaning without too much trouble. DO NOT use too much vinegar or the bead may soften or dissolve.