Post subject: HPHT Treated Diamonds - SERIOUS ALERT
Posted: Wed Jan 27, 2010 2:51 am
Valued Contributor
Joined: Mon Sep 11, 2006 7:11 am Posts: 102 Location: Cape Town
I am coming across more and more people who have bought HPHT treated diamonds that have been passed as natural. The lastest was a person paying in the region of R250 000.00 ($33 400) for a stone that had been treated.
There doesn't appear to be a lot of reference material for identifying these stones. I do subscribe to GIA and there have been some interesting articles which have helped considerably, but not enough. I believe even the experts in some of the large reputable labs around the world can have trouble identifying this material. Some of the sophisticated equipment available today can't always ID these stones and at the end of the day it appears to revolve around examining the interference patterns between crossed polars and analysing them correctly.
This is absolutely imperative for the diamond dealer and valuer to get educated on this before a very costly mistake is made. Has anyone come across any photomicrographs of the natural and treated stones?
from what I understood, HTHP treated diamonds are very hard to detect, even when using laboratory techniques. Is that true? No way to spot them out of the lab?
I also heard that in most cases, irradiated diamonds can be detected out of the lab neither, but that sometimes the hand spectroscope might help, what about it?
Joined: Mon Sep 11, 2006 7:11 am Posts: 102 Location: Cape Town
cascaillou wrote:
from what I understood, HTHP treated diamonds are very hard to detect, even when using laboratory techniques. Is that true? No way to spot them out of the lab?
I also heard that in most cases, irradiated diamonds can be detected out of the lab neither, but that sometimes the hand spectroscope might help, what about it?
HPHT can be difficult to ID. If the diamond is refered on the Diamond Sure as a type ll I first check to see if the stone transmits Short Wave UV, if so then we know we are dealing with a type ll stone. The next is to examine the stone side ways (through the girdle) looking through the pavillion to see the interference pattern. As I understand it, if it is a low order brown and blue appearance with tatami it is natural. If the interference patterns are a high order then refer it to a lab for further testing. Bright colours like orange blue gren etc.... muct refer. Most the stones I check are low order. By the way if you see the intersecting Tatami effect, you know the stone is natural and not synthetic. GIA Gems and Gemology Vol XLV Summer 2009 have a very good article.
As far as irradiated diamonds are concerned, I always refer them to EGL in Johannesburg for testing. hey have the brains and the equipment to check them thoroughly.
looking through the pavillion to see the interference pattern. As I understand it, if it is a low order brown and blue appearance with tatami it is natural.
please, do you know of a link detailing the interference tatami things (with pictures if possible)
Joined: Mon Sep 11, 2006 7:11 am Posts: 102 Location: Cape Town
cascaillou wrote:
Quote:
looking through the pavillion to see the interference pattern. As I understand it, if it is a low order brown and blue appearance with tatami it is natural.
please, do you know of a link detailing the interference tatami things (with pictures if possible)
My apologies for the delay in getting back to you. I am away at the moment, so i'll find a link or post some pictures next week when i'm back.
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