Diamond GradingImitations and Synthetic Diamonds
Synthetic and simulated diamonds are natural diamond substitutes that are often used in low cost jewellery. The main reason for their use is their very low cost, and there are sacrifices involved when getting a simulated or synthetic over a real natural diamond.
Laboratory created diamonds, also known as synthetic diamonds, are chemically identical to natural mined diamonds, but are grown using accelerated techniques in labs, not deep underground over millions of years. Such diamonds are substantially cheaper than mined diamonds, but they still exhibit the same chemical and physical properties, including hardness and refractive index. Clear and white, jewellery grade synthetic diamonds are much more difficult to produce than low quality industry grade ones. Most synthetic diamonds are used in industrial applications where the aesthetic qualities of the stone are unimportant and only its extreme hardness matters. In fact, synthetics are critical for industrial use, since mined stones alone would not be able to fulfill the growing demand for the diamonds as abrasives. Gem quality diamonds were very rare until very recently, and even now there are certain limitations on how clear and colourless they are. In addition, because the techniques used for created synthetic diamonds are very different than the natural process of carbon crystallization, the inclusions and colour shades of synthetics are easily distinguishable from mined diamonds. All synthetic diamonds are required to be marked as such at the point of sale.
Simulated diamonds are natural or synthetic compounds that resemble diamonds visually, but are different in their chemical and physical properties. They do not have the hardness of diamonds and usually will not have as much sparkle (for stones of comparable cut quality). One of the earliest imitation diamonds was lead glass, which has a high refractive index, but is still considerably softer than a diamond. Today such glass is often used in jewellery and is known as rhinestones or Strass. They are not considered important diamond imitations since they are very easy to differentiate. Most common imitations today are cubic zirconia and moissanite. Both are synthetic crystals that look very similar to diamonds to an untrained eye, but can be distinguished by means of simple tests by a jeweller. Cubic zirconia, or CZ, has a very similar refractive index to a diamond and even better dispersive qualities, causing it to show more rainbow effects than real diamonds. At the same time CZ is relatively soft, 8.5 on the Mohs hardness scale compared to diamond's 10, which makes this stone easily scratched and damaged. Moissanite has a hardness of 9.5, which makes it much more scratch resistant, but it also displays a somewhat different pattern of light refraction and dispersion, most importantly, it has the ability to refract light at two different angles, causing the facets of the stone to appear doubled when observed through the table.
All jewellery that appears to have diamonds has to clearly specify whether the diamonds are mined, synthetic, or simulated. The difference may not be obvious at first sight, but it will become increasingly apparent over time as the low quality imitations start to show scratches, chip off, or change colour.
