Examining a diamond

Details Examining a diamond Examining a diamond

1997-06-06

1999-03-09

Hannaher, Constantine

Radiant energy

Invisible radiant energy responsive electric signalling

Ultraviolet light responsive means

356 30, G01N 2187

Patent

active

058805044

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND TO THE INVENTION

The present invention relates to a method of and apparatus for examining a diamond. For example, the invention may be used to test whether a diamond has had a layer of synthetic diamond deposited thereon. This is of particular importance in detecting whether the diamond comprises CVD diamond material and also in locating such material if present.
Over the years, a number of methods of synthesising diamond material have been developed. One of these methods is the chemical vapor deposition (CVD) technique, which is a low pressure technique involving deposition of synthetic diamond (referred to as CVD diamond material in this specification) onto a substrate from a gas.
The synthetic diamond material may be deposited on an uncut or part-worked natural diamond which is then worked, for example, into a round brilliant cut. Alternatively, the synthetic diamond coating may be deposited onto a fully fashioned brilliant stone after working of the stone. The thickness of such a synthetic diamond material layer may be very thin--it could be in the range from 1 .mu.m to 0.1 mm.
The value of a diamond is in part dependent upon its weight. Accordingly, synthetic diamond material such as CVD diamond material may be deposited onto natural gem diamonds, before or after cutting of the diamond, to increase the weight of the finished product. A diamond artificially enlarged by deposition of CVD diamond material is referred to in this specification as a "CVD
atural diamond doublet".
However, the value of a diamond also resides in its qualities of authenticity and uniqueness and in the fact that it is an entirely natural product. Thus, a diamond that has not been enlarged by deposition of synthetic diamond material has a value over a CVD
atural diamond doublet.
CVD diamond material may be deposited on a non-diamond or diamond substrate. In the latter case, the CVD diamond material can replicate the structure of the diamond substrate (referred to "homoepitaxial growth"). The CVD
atural diamond doublet produced can be identical in appearance, density and other common physical properties to an entirely natural diamond and there may be a problem in identifying such a CVD
atural diamond doublet.
It is an object of the present invention to provide a method of and apparatus for testing whether a diamond has had a layer of synthetic diamond deposited thereon.
It is desired that the apparatus should be simple and inexpensive and may be put into operation by a person with relatively little training. The method and apparatus should be capable of being operated reliably and consistently by a practised jeweller who has no training in laboratory gemological analysis.


THE INVENTION

The present invention provides a method of and apparatus for testing whether a diamond has had a layer of synthetic diamond deposited thereon, as set forth in claim 1 or 3. Preferred and/or optional features of the invention are set forth in claims 2 and 5.
The present inventors have discovered that if there is a difference between the surface area of the region of a diamond that strongly absorbs radiation substantially of wavelength substantially in the range 230 nm to 320 nm and the total surface area, a synthetic layer is present. Such radiation is substantially unabsorbed by the synthetic part and penetrates through it to the underlying natural material, where it will normally be absorbed. Synthetic diamond material, if present, will normally be deposited onto an area of a diamond and, unless that area is a re-entrant in the surface of the diamond, will tend to increase the surface area of the diamond. As the layer may be very thin (depth of the order of microns) the net increase in surface area may be very small, but is nevertheless detectable with sufficiently sensitive equipment.
An integrating enclosure provides a particularly effective way of measuring the surface area of the region of the diamond strongly absorbing the radiation of interest. The interior of the integrating enclosure is irradiated such that the irradiatin

REFERENCES:
patent: 5164586 (1992-11-01), Hohberg et al.
patent: 5536943 (1996-07-01), Smith et al.

Affiliated with

Also associated with

Rating

Examining a diamond does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Examining a diamond, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Examining a diamond will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1324208