I’ve written to you recently, warning about the trend of coating tanzanite.
This beautiful stone is often coated with a substance that enhances its colour (and thus, its value). The problem, of course, is that this process is not disclosed, so gem buyers are duped into paying more for stones than they are actually worth. Tanzanites are not the only victim of this procedure.
Blue topaz is the latest gem to fall prey to this alarming trend. And these stones are not alone. We regularly see precious stones such as quartz and beryl, as well as the aforementioned tanzanite and topaz, being coated and passed off as gems of much higher value than they can actually claim.
How It’s Done
It has been the norm to only coat the pavilion. But newer con artists have coated the entire stone. I’ve seen this on both tanzanite and topaz that have come in to be assessed and certified..
An Ancient Art
Gem enhancement has been practised for centuries. As long as people have been finding and selling precious stones, they’ve been looking for ways to get more from each sale. In fact, one could argue that this very goal is what motivated the first jewellers to cut and polish the earliest stones!
We spoke last week about oiling gems, and how this can affect the appearance of emeralds. Oiling is just one of many treatments, however. From colouring the back of gems (using a range of means and materials) … to foil-backing … to the far more sophisticated methods we see today, enhancing gemstones in any way possible is a pervasive trend.
It’s Okay – If You Know (And If It’s Natural)
When it comes to gemstone treatments, there’s a simple rule: If a gemstone treatment duplicates a natural process – and the results are permanent – it does not have to be disclosed. For example, sapphires undergo natural changes in heat and pressure which enhance their incredible colour. These processes can be mimicked in laboratories – with the same results.
On the other hand, some untreated kunzite can fade after just four hours in the sun.
Most tanzanite mined is brown. It is converted to blue through heat treatment. This treatment duplicates a natural process. And it’s permanent.
HPHT treated type ll diamonds that are mined brown can be changed to white through high pressure, high temperature treatment (hence HPHT). But interestingly has to be disclosed even though it duplicates a natural process and is permanent.
Conceal vs Reveal
But the treatments we’re seeing at the moment on blue topaz (as well as the quartz, beryl, and tanzanite we’ve mentioned) fall into a different category. These are not natural processes. And very often, they’re not permanent either. Unscrupulous jewel traders misrepresent the value of their wares by altering their appearance.
Modern techniques are so sophisticated that it can be very difficult to detect the treatments – even for experienced gem buyers. Unfortunately, ignorance is not a defense in this case. Lawsuits can – and do – happen when unsuspecting customers discover they’ve been duped into buying something worth less than they paid for it. And often this only happens years after the sale!
This is why it’s so important to assess any gemstones you plan to sell. An expert certification gives you the peace of mind that you’re selling only the best quality, and that your business is safe from litigation.
Call us on 021 761 1746 or email jeremy@gemlab.co.za to find out about the latest gemstone cons, and to have your gems certified by SA’s leading gemmology lab.
