New Treatment For Diamonds

(via ICA Lab Alert No.7, August 13, 1987) Nubo Horiuchi writes:

Source
I found this treatment in January 1987.

Status
This treatment makes cleavage cracks to the surface less visible by impregnating with unknown material. On looking through the cleavage crack of a diamond treated in this manner, a whitish appearance can be seen which improves the clarity grade of the diamond. Impregnating the cleavage crack of the diamond with this unknown material, which may be silicon oil, it is quite effective in improving the appearance of the cleavage crack because it reduces diffuse reflections. This treatment was located in the diamonds lots imported from Israel.

Identification
Upon looking through a diamond under a diamond light, a dark blue or rainbow hue of interference color will be seen under the diffused light.

Opinion
The organization of gem laboratories in Japan judges that diamonds enhanced in this manner are treated diamonds.

E.Gubelin writes:
It certainly is imperative that all members are informed about this new unethical treatment of diamonds because too many dealers might consider these artificially filled fractures as naturally lined fissures.

Youichi Horikawa writes:
I think identification of these treated diamonds is not easy, because the interference color can be seen in untreated diamonds also.