We see too many burnt and damaged gemstones in the lab due to negligence.
We had three tanzanites come in, in one month that had been damaged by ultra sound cleaning. Tanzanite should NEVER be put in an ultra sound. The one client said he had been putting tanzanite jewellery in an ultra sound for years and nothing happened. A very expensive lesson learnt on this occasion.
We wanted to know how much heat a synthetic moissanite could take before the surface showed any damage. It turned yellow and looked cloudy and then went back to its original white colour.
It was only after the forth time under the torch that it showed surface damage. You can judge the temperature for yourself. After the burn we boiled the stone in sulphuric acid to clean it.
Top: These picture are of the synthetic moissanite surface after it was burnt.
The effect is very similar to a burnt diamond.
Accredited Senior Gemologist