Oiled Tanzanite
Over the past five years, gemologists at Bangkok’s Lotus Gemology have seen increasing numbers of what we might call “non-traditionally” oiled gems. This is particularly true of, but not limited to, Burmese gems such as ruby, sapphire, and spinel. But it is important to note that any gem with surface-reaching fissures can be oiled, often with dramatic improvements in apparent clarity. Cuprian and rubellite tourmalines are also frequently enhanced in this way.
Recently we received a faceted tanzanite weighing more than 100 carats for testing. As is our practice for non-emeralds exhibiting fissure-filling clarity enhancement, we photograph the gem and then allow the client to resubmit the stone after filler removal. The figure above clearly shows the dramatic effect that fissure filling with oil/resin can have on gems such as tanzanite, even where the refractive index of the filler does not closely match that of the gem.
