identifying synthetic and treated diamonds

Because synthetic diamonds have identical properties to natural diamonds, it is almost impossible to determine a synthetic stone through a visual examination alone, although there are several ‘clues' that if apparent in the stone can indicate the synthetic nature of the diamond and should be submitted to a lab for further gemological investigation into the stone's origin. These clues though are by no means fool-proof and are simply indicators. Identification of the synthetic nature of a diamond requires a trained and skilled gemologist who is trained in handling special equipment available in leading gemological laboratories such as International Diamond Laboratories.

visible clues
The structural distinction between natural and synthetic stones can be found in the difference of the diamonds' crystallization conditions and the chemical composition of their environment. Rough, natural crystals are found in different shapes, the most common being the cubo-octahedron. The cube, rhombic dodecahedron and tetrahedron are also found.
Synthetic diamonds are almost always cubo-octahedrons and have a characteristic tabular appearance. Another visible clue is found in HPHT formed diamonds. The ‘seed' crystal from which the diamond is built upon can sometimes be visible.
However, once polished, these cubo-octahedral faces will not be visible any more, making the synthetic diamond very difficult to detect visually.

in the lab
Metallic inclusions are also found quite often in synthetic diamonds, yet are never found in naturally produced diamonds. The inclusions manifest themselves in a variety of forms and are characterized by their metallic gleam. By using Energy Dispersed X-Ray Fluorescence the nature of the metallic inclusions can be determined. Synthetic diamonds can also display a slight magnetic behavior due to the presence of the metallic inclusions. Growth surfaces may take up impurities at intersections and they reflect the external morphology and are usually the only way to recognize the synthetic nature of the crystal within a polished stone. The combination of cubic and octahedral internal growth sections may create typical growth line indicators in a synthetic stone. These show up as an ‘hourglass' or ‘stop sign' pattern.
Color zoning may also be found in synthetically produced diamonds. This is caused by a local and temporary variation of the coloring element during the stone's creation.

DTC DiamondView and cathode luminescence
The difference in the growth process of a synthetic diamond compared to a naturally produced diamonds can be identified using either of these two methods. The cathode luminescence uses electrons to highlight the stone's complex structure while the DTC DiamondView uses a camera to view the fluorescence pattern created on the surface of a polished stone with intense short wave ultraviolet light. Nearly all near colorless HPHT synthetics show phosphorescence - an afterglow - when the ultraviolet lamps are turned off. A definitive identification can then be made by observing the fluorescence patterns characteristic of near-colorless synthetics.
The polished facets of a synthetic diamond intersect the internal growth faces of the stone. In the DiamondView(tm) instrument, each type of growth face has a distinct fluorescence color that gives the synthetic its characteristic fluorescence pattern.

the DTC DiamondSure
The majority of synthetic diamonds have an intense yellow to orange-brownish hue because of the presence of nitrogen atoms in the stone's crystal lattice. In naturally occurring diamonds, these nitrogen atoms mostly occur in groups but in synthetic diamonds they are isolated. This difference can be viewed using visible or infrared UV spectrophotometers. The DTC DiamondSure utilizes these methods providing a quick and easy result that immediately highlights the possibility of the diamond being synthetic. It should be stressed that this is only a screening method and is by no means capable of identifying synthetic diamonds. The diamonds are placed table down on a measurement probe and the visible absorption spectrum of the stone is measured and analyzed with proprietary software. Within seconds the results are visible on the machine's screen indicating whether the stone is a natural diamond or whether the stone has indicators calling for further inspection (in most cases the stones are then subjected to further analyses by the DiamondView for a guaranteed result). Not all stones though that are flagged by the DiamondSure are synthetics; rather they display indicators that warrant further examination.