I have been concerned for a while about the amount of treated Welo opal being passed off as natural black opal. There are numerous treated Ethiopian opals wrongly listed on the internet. Equally important they are also been sold in Australian retail shops and unfortunately also on the opal fields. I asked Natasha Patel, an honours graduate in gemmology (AIGS Thailand) to research on how to tell if the stone is natural or treated one is on the opal fields and/without access to laboratory testing equipment.
This is a copy of Natasha Patel’s research report – Natural Black Opal – Are You Asking The Right Question?