Martin Rees, Jeweller and Pawnbroker

PVD (Physical Vapour Deposition) - Coated Gemstones

These stones have appeared recently.  They offer brilliant colours at a reasonable price, and iridescent effects which are not available in natural stones.

Sometimes we find the owners are not aware the stones are coated.  This is serious because these gems have introduced some new problems.  The coatings have variable quality.  The best are durable, and very unlikely to break away from the stone.  With care, the coating should last as long as the setting.  But read on, and make sure you understand how to look after these beautiful stones.
Lower quality stones are appearing, and their quality can be poor.  They can be damaged by sunlight, or alcohol wipes.  However we have seen none as yet.

Identifying PVD - Coated Stones.

An experienced jeweller should be able to advise you.  Whenever a stone is described with a name you don't recognise, check it, as often, coated gemstones are sold under special names.  The Internet or a jeweller will be able to help.
Currently most stones treated are topaz, clear quartz and C.Z. but the market is changing all the time so others may appear.

What are the Benefits?

In the first place the coatings make vibrant colours possible; colours which don't occur in natural stones, at least as a reasonable price.  The treatment involves applying an extremely thin layer of a specific chemical to the stone.
The other popular effect is iridescence, which is achieved by applying an even thinner layer, often titanium;  then refractions within the layer produces iridescence - it's an effect similar to an oil film on a wet road.
The best manufacturers make sure the coatings are durable and bond strongly to the gemstone, in addition they choose coatings which are tough, and which will last as long as the settings, provided reasonable care is taken.

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Looking after these Stones.

Often the coating is only applied to the back of the stone which reduces the risk of damage.  However we cannot be certain this is always the case.  If the stone is chipped the damage will be more serious than with a normal gemstone as the coloured layer will be lost at that point.  However with care the coating will last as long as the setting.  But often we see old stones where the back has been chipped, so do take extra care especially when these stones are mounted in rings.
Iridescent stones will be spoilt by any scratches.  So these stones should only be worn on recreational occasions, and certainly not when doing any form of manual work, and that includes washing up!
Eventually they will need cleaning.  It is difficult to give you the correct advice because the coatings vary both in chemical composition and in quality of application.  If at all possible contact the seller for guidance; if not follow the advice here.  But understand this is purely advice for which we aren't charging so we cannot accept any responsibility if a stone is damaged when you clean it.  There is always the risk that poorer quality stones may appear at any time, which will not be able to withstand even the gentle treatments recommended.
It's easy to tell you what you must NOT do.  Do not attempt to polish the jewellery; that includes rubbing it with a jewellery cleaning cloth.  Never use an ultrasonic tank (although you will often get away with such treatment) to clean it.  And acids are strictly out.
To clean, soak the piece in warm water with just a dash of washing-up liquid.  Any stubborn dirt should be removed with a very soft brush.  Is it better to soak for a long time or use more pressure from the brush?  Unless the chemical composition of the coating is known it is impossible to give advice.
Iridescent stones need even more care.  The beautiful effect is produced by refraction within the coating.  Anything on the coating will spoil the effect.  This includes grease, either from your skin or from the washing-up.  Even water drying on the stone will leave a small deposit and spoil it.  So dry the jewellery on a paper towel to absorb the water.  If necessary give a final rinse in de-ionised water.

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Repairing Jewellery which Includes Coated Gemstones

These stones will not stand up to the cleaning required after repairs.  So most jewellers will not do any repairs, including ring sizing.
If a stone is lost or damaged, replacement may be impossible, as the coated stones are often not available through normal trade sources.  You would have to return them to the original supplier.

The Second-Hand Market

Because there are problems with the stones durability, and repairs are impractical, our offers are rather disappointing.  After we buy the jewellery, it is cleaned and polished.  So if the stone is low quality, it may be damaged, and then we have to scrap the piece.  That's why we cannot pay high prices for coated stones.
Our customers can buy with confidence.  The stones have been tested first by the original owner, and then thoroughly cleaned in our workshop, so they must be durable.  The new owner must still exercise the usual level of caution as described here.  But with reasonable care, the jewellery will have a satisfactory lifespan.  And at our second-hand price, they are great value.

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