Buyer Beware; Stone Coatings – A hoax?
Some manufacturers try to improve the quality of inferior stones by coating the stone with a “film of diamond-like carbon known as DLC”. In fact, what this does according to Wikipedia is “… quench down the fire of Cubic Zirconia…” Fire in layman’s terms is sparkle. According to Wikipedia “its refractive index is high at 2.15–2.18 (compared to 2.42 for diamonds)” and “its dispersion is very high at 0.058–0.066, exceeding that of diamond (0.044)”. Without getting more technical, Cubic Zirconia has more sparkle than mined diamonds! I certainly don’t want to tone that down.
Some jewelers will claim they coat their synthetic or simulated stones with a very thin layer of diamond. No matter what they call it this is known generically as “amorphous diamond”. This results in “an upper layer that is both simulant and man made diamond”. This does nothing for the quality of the stone’s clarity, cut or hardness. Simply stated, put a new coat of paint on an old jalopy car and it will still dent and not run well. Coatings don’t help the beauty of the core stone. In fact, it is not even a coating because the process results in a layer that is both the original stone and a vapor of man made material. Some inspections by industry watch-dogs state it was “…an unidentifiable coating.”
Diamond-like carbon (DLC), in mineralogy known as Amorphous Carbon, is the name used for coal, soot and other impure forms of the element carbon that are neither graphite or diamond. The coating places or only mixes particles with the top layer of the Simulant Diamond Molecules that are less than one fifth of a human hair end. This is only enough to diffuse light.
In fact it prevents light from shining into the diamond by reflecting light from the outside. Diamonds get their brilliance, sparkle and fire from light penetrating into the stone and bouncing off theinterior facets. It is like placing a chrome tint over your car windows, thus preventing light from entering the stone.
The claim that coatings add hardness to the stone are confusing at best. If it is a complete coating then it may extend some resistance to abrasive wear. But since it usually is an infusion of diamond like carbon and does not completely coat the surface, abrasion will still readily occur. While some small degree of scratch resistance may be detectible with scientific equipment, on a practical level of day to day wear, it is my professional opinion that no genuine resistance to abrasion is achieved.
Finally, DLC or Amorphous carbon is not designed to strengthen for impact. So if you bump your stone against something it has no more “hardness” or protection against breakage than an untreated stone. No practical measure of protection is achieved. All stones can chip even Mined Diamonds.
A discussion about diamond coatings would be incomplete if it did not address the coloring of stones. Some stones are coated with a color (yellow, pink, black, etc.). The coating can be used to hide imperfections and impurities in the stone. Be careful since colored stones with colored coatings can hide cloudy stones and stones with poor fire and sparkle.
My advice is to just buy a great quality Synthetic or Simulated Diamond, without any gimmicks, from a jeweler you trust.
Originally Shared Suzan Flamm MJSA