Numerous sapphires coming out of Bangkok that look like nice padparadschas have been diffusion treated, according to a study conducted by the AGTA Gem Testing Center.

“They’re Madagascar pink sapphires being diffused with oxygen, and quite possibly something else, giving them a distinctly orangey appearance,” says GTC lab director Kenneth Scarratt. “Every stone looked at [while] immersed in methylene iodide against a diffuser plate shows a distinct rim of orange color around the stone.” This is not the same appearance shown by blue diffusion-treated sapphires, which display color concentration at facet junctions. “This so far has not been seen in these ‘padparadschas,’ ” says Scarratt. Most of the sapphires tested were approximately .50 ct., but larger sapphires—up to 4 cts.—have been treated as well.

Scarratt notes that buyers of this type of material should immerse these stones in a liquid such as methylene iodide and, with the aid of a diffuser plate, look for any orange and pink color concentrations. If orange color concentrations appear to form a rim that follows the three-dimensional outline of the gemstone, seek further advice from a gem laboratory.