In answer to the lack of forthright disclosure on the part of
dealers it is a global phenomenon. I personally believe it to have a
two-fold cause. First, treatments or more accurately successful
treatments constitute a source of competitive advantage. So in the
same way that Coca-Cola does not disclose the recipe for Coke your
average burner who figures out how to turn the sows ear into a silk
purse is not going to casually discuss it. Secondly non-disclosure is
frequently motivated by fear. The fear being that if you as a
customer were to find out the beautiful gem or rough in your hands
started out life as a sows ear, you'll be far less likely to put a
large pile of cold hard folding money on the table to buy it.
In answer to the question regarding radiation source I will reply
with yes to all three forms mentioned by Mr. Galarneau, Cobalt 60,
cobalt 66, or linear accelerator. As to where it's done, it's done
everywhere and anywhere a savvy stone dealer has access to a smart
Linear acceleration does not generally produce residual radiation
that would be above background levels at the time of sale. Which
means its safe. I don't know about Cobalt treatment I would be very
surprised if there is any residual radiation above background present
in treated tourmaline.
In my own case I will occasionally try to burn the brown out of a
Namibian pink tourmaline with heat alone. I have no first hand
experience with irradiation of the material, my knowledge being from
the available literature on the subject and through conversations
with other dealers. My success with removing brown from pink
tourmaline is at best mixed. The reason is simply this; the chemical
variation in Namibian pink tourmaline is so great that the critical
temperature is essentially unpredictable, heat it too hot and it
For people with a keen interest in this subject I would urge the
purchase of Kurt Nassau's 1984 volume entitled gemstone Enhancement.
It remains an excellent basic text on general gemstone treatments.
I will also be exhibiting an excellent selection of calibrated
Namibian DEMANTOID garnet in Room 153 of the Pueblo Inn starting on
the 2nd of February.
PO Box 354 ~ Omaruru ~ Namibia