Oil treatment has a significant impact on the appearance of an apatite.
Lotus Gemology warns that oiled rubies, sapphires and spinels are entering the Bangkok wholesale market in increasing numbers. Most, but not all, of these gems are originating from Burma.
When a red spinel and a tanzanite were submitted for testing, oil was found in the fissures. Removal of the oil resulted in a startling deterioration in clarity.