a publication of the International School of Gemology 7 January 2016

Black Diamond or Created Moissanite?

It’s one of the hottest items in the current jewelry market: black diamond. The very name conjures up dreams of exotic places and people. But what really is a “black diamond” and how do you know you are getting a true black diamond and not an imitation like created black moissanite?

First, authentic natural black diamonds are rare. The conditions at which carbon crystallizes causes all of the carbon to crystallize. So the concept that black diamonds are made of uncrystallized carbon is not totally accurate, based on current scientific report. Most black diamonds are actually low quality diamonds that have been irradiated to create a very, very dark green color that appears black. Some are simply regular diamonds that are so heavily included that they appear black. Whatever the source, black diamonds are hot on the market and many have asked how to separate black moissanite from black diamond. Here are a few “tells” we have found that may be of assistance in the effort.

The first involves the sheer nature of the materials. As you can see below, irradiated black diamonds are made from low quality diamond crystals. As a result of the low starting quality, and perhaps what happens to these diamonds during the irradiation process, the diamonds are very grainy with light and dark colors throughout, and as seen in the image below right there are surface breaking fissures that are easy to see.

Created moissanite, however, is almost glass-like. The lab created material is pristine and uniform, therefore presenting a far different look through magnification than most black diamonds.

As seen below in overhead light reflected off the table surfaces, the created moissanite has a mirror-like surface while the black diamond has surface reaching fissures and pits. This is your first “tell” to separate created moissanite from black diamond….the formation or structure of the stone itself.

Presidium Reflectivity Meter

I had to wipe the dust off of our Presidium Reflectivity Meter for this demonstration, and it proved a worth-while effort. Although our Jemeter Digital 90 is our main tool for gemstones with refractive indices that are over the limit of the traditional refractometer, the Presidium Reflectivity Meter proved a diagnostic tool for separation of created moissanite from black diamond. At left is the reading scale that flips up on the meter. You simply place the stone over the aperture of the meter and press the button. Instantly, this gizmo is able to diagnostically separate our black diamond from our black created moissanite. Below you see the actual readings of our black gemstones on the Presidium Reflectivity Meter.

Jemeter Digital 90

The jewelry industry lost a huge opportunity to make gem identification easy when we failed to fully comprehend the value and usefulness of the Jemeter Digital 90, which has been out of production for many years now. This is also a reflectivity meter as the Presidium above, but with the added value of a software interpretation of the readings that provides for an actual refractive index reading. As you can see below, the Jemeter Digital 90 gave us readings that are virtually textbook for the refractive indices of these two gemstones. Another “tell” in the separation of black diamond and created black moissanite.

Raman Spectroscopy

Below are actual Raman scans of created moissanite, natural diamond and irradiated diamond. The created moissanite is from the RRUFF files, and two diamond scans from the ISG archives. As you can see the difference in Raman peaks for the created moissanite is significantly different than the natural diamond or the irradiated diamond. This makes for an easy separation of the gemstones using this technology.

Below are Raman scans of the created black moissanite and black diamond shown above in this newsletter. As you can see, the separation is quite easy using Raman Spectroscopy. For those interested in Raman technology for your lab, there is now a very cost effective, yet highly accurate Raman available on the market from the Gemlab folks of the Canadian Institute of Gemmology. Click here to learn more: Gemlab GL Gem Raman

After reviewing many irradiated black diamonds and created black moissanite, it became clear that an experienced gemologist with a good microscope and fiber optic light can separate black diamond and created black moissanite simply on the structure, as seen at the top of this newsletter. However, for more in-depth verification, the Presidium Reflectivity Meter and Jemeter Digital 90 provide cost effective diagnostic results. For those of you who would like to take advantage of the lower cost of Raman technology that has been designed for the jewelry and gemology industry, we strongly recommend the GL Gem Raman as this new technology has far greater applications than simply this subject. Given the very affordable price and the technical support available from the Gemlab organization, there is every reason now to add this technology to your gemological lab or jewelry buying office.

We should note that there are other black stones out there that emulate a black diamond and those will need to be covered in a follow up report. For now, we hope this is of assistance to those who want to be sure you are dealing with authentic black diamonds and not created black moissanite when you make your purchase or sale.

Robert James FGA, GG
President, International School of Gemology

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