Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Troy Ardon and Garrett McElhenny for GIA Lab Notes wrote:
Quote:
Figure 1. Face-up image of the natural diamond with CVD synthetic diamond overgrowth. The blue color is due to the boron-doped CVD layer. Photo by Robison McMurtry.
A 0.64 ct Fancy grayish greenish blue cushion modified brilliant (figure 1) was recently found to be a composite of synthetically grown and natural diamond. During testing, the infrared spectrum showed both strong absorption of nitrogen and the absorption of uncompensated boron, features characteristic of type Ia and type IIb diamonds, respectively (figure 2). The UV-Vis-NIR spectrum showed “cape” peaks, which are nitrogen-related defects, but also a sloping absorption into the red portion of the spectrum caused by uncompensated boron. It is very unusual for boron- and nitrogen-related defects to be seen together in natural diamonds, though an example has been seen before (Spring 2009 Lab Notes, pp. 55–57). Mixed-type diamonds always call for additional scrutiny.
Post subject: Re: CVD Layer Grown on Natural Diamond
Posted: Sat May 11, 2019 5:06 pm
Moderator: Lapidary Diamonds
Joined: Mon Aug 20, 2012 11:32 pm Posts: 1747 Location: Florida, United States
Repolish the stone and the yellow or brown coloration would be evident. This cvd on single crystal diamond is fraudulent and only someone criminally inclined would participate in it.
Not Type 2B cvd on type 1A substrate in nature. What GIA observed before was an interstitial mix of both nitrogen and boron in the same diamond and that is quite rare.
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