ADAMAS GEMOLOGICAL LABORATORY publishes gemologically oriented software for the jewelry appraiser, jeweler, or student in gemology or mineralogy. The laboratory also provides technical consulting and jewelry appraisal services to the trade and the public and expert witness services to the legal profession.

 

GEMKEY SYNTHETIC DIAMOND ARTICLE

This article (after editing) was published in
GEMKEY magazine Volume One, Issue Two

Will The Next Diamond You Sell Be Synthetic?

by Martin D. Haske

The more pressing question, is whether or not you will know what you are selling...........

But you are a jeweler, a gemologist,..you should know about what you are selling, shouldn’t you?  The courts and consumer protection laws seem to think so.  So what’s the problem, we’ll just send every stone to a laboratory for a “cert”.  What about that parcel of 5 pointers we just bought?  Or that great deal on one grainers?  Do we have to send each stone out to a laboratory?  Will we have to invest in more sophisticated equipment? Will we have to take courses to learn what’s new in the industry..  The answers to these questions are swiftly shifting from maybe to YES, all of the above, and then some.

The last decade has seen a shift in the global economy, where technologies once dedicated solely and unconditionally to the defense industries throughout the world are being rapidly shifted to produce products to bring in hard currency, in order that those working in those industries can get paid and put bread on the table.  For years now, synthetic diamond production has been a mainstay in providing inexpensive material for drilling, cutting and polishing industrial applications, among others. Single crystals over one carat are now routinely produced in gem quality colors.  Processes have advanced such that thin films of diamond can be grown which are inches in diameter and millimeters thick, a potentially interesting source.of rough.

Recently, we have seen metal catalyst diamond production techniques utilized to produce near gem quality synthetic colorless and colored diamonds  These diamonds appear to be mainly produced by facilities in the former Russian republics that were once dedicated to the needs of the space race...Most, if not all of the near colorless and colored diamond produced in Russia and trickling into the marketplace, appear to be of the nickel catalyst production technique.  Happily, these diamonds materials are generally readily distinguished from their natural counterparts by visible range spectroscopy, fluorescence and phosphorescence and more recently, in the case of the near colorless type IIa material by their electrical conductivity characteristics, properties brought to light because of the flap over the introduction of synthetic silicon carbide (moissonite) into the market as a diamond look-alike or substitute.

In the last few years DeBeers came out with the DiamondView and DiamondSure, sophisticated instrumentation, the simplest of which looked for the existence of N3 absorption (the 415nm line).  Since , according to the literature, approximately 99% of natural diamonds (type Ia) have this feature, the majority of which may be deduced at room temperature, the DiamondView as well as the author’s SAS2000 Spectrophotometer Analysis System served as a good indicator that the diamond not showing this characteristic (415 absorption) could possibly be of synthetic origin, and should be examined further.  With nickel catalyst type Ib’s, definitive nickel related absorption lines could be detected with the SAS2000 and possibly with a visual spectroscope. It might be noted that the subset requiring further study would also include some D color type Ia diamonds as well as all Ib’s and all type II’s.

The crystal ball of what the future may hold in regard to synthetic diamonds, can, surprisingly, be found on the Internet.  One the best resources is the IBM patent server, containing images of all United States patents issued since the early 1970’s as well as patents in Europe. The URL for this site is http://patent.womplex.ibm.com/.  Among the most interesting patents include that for the irradiation treatment of diamonds to produce purples/pinks/reds (US4,950,463 Purple Diamond And Method Of Creating Same).  This patent contains a wealth of information not found in gemology texts relating to the treatment of synthetic type Ib material (as well as natural).

Last February in Tucson I gave a lecture at the NAJA conference on spectrophotometry, the last slide of which contained reference to US patent(s)  #4124690 and #4174380.  These patents entitled “Annealing Synthetic Diamond Type Ib” and  “Annealing Type Ib Or Mixed Type Ib-Ia Natural Diamond Crystal” were issued in the late 1970’s and dealt with the heat treatment (annealing) of diamond resulting in the conversion of Type Ib nitrogen (not aggregated) to Type Ia nitrogen (aggregated).  Aggregation of free nitrogen which causes color to paired nitrogen which do not cause color as well as the aggregation of free nitrogen to N3 centers (three nitrogen atoms), both of which cause color, are the logical applications of the information in these patents, and theoretically pose the biggest problems for the jewelry industry in the not so distant future, if not today.

What does all this mean, you ask?  It means, in the first place, that since synthetic diamond production techniques have progressed to the point that 0.25ct and above stones can be produced in VS clarity grades, eliminating the telltale signs of metallic inclusions which hint at synthetic origins during the normal grading process, that the trade laboratories will have to, and should immediately, employ multiple screening techniques when grading ALL diamonds for the trade.  Cost effective techniques currently include electrical conductivity using high resolution electrical leakage tester (not breakdown voltage), the only currently available one being the Moissketeer 2000SD, short wave phosphorescence using standard UV tubes and viewing boxes like those supplied by GIA, and room temperature spectrophotometric screening, such as that provided by the SAS2000.

These same currently available techniques can and should be used by retail establishments as a limited protection against the unknowing sale of synthetic goods. It is best to get into the habit of screening even if it may not be 100% reliable, given the pace of technology today

In the lab, cathode-luminescence screening such as that using the DeBeers’ DiamondView, is currently limited to a few select laboratories, and ultrahigh resolution spectrophotometric testing, including chilling the diamond, may be too time consuming.

Again, none of these techniques may be entirely diagnostic in the near future, considering the advancement of production methods and the continuing emergence of new treatment techniques.
 



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