While I am not defending the labs whose certificates cannot be trusted, I feel when it comes to price differences of diamonds, people selling diamond jewellery should be aware that there is more to determining a diamond's price than just the colour and clarity.
It seems there is a trend dictating that because a diamond has a certificate it means it is a good quality stone. Labs grade and certify diamonds regardless of the quality.
When comparing the price of diamonds with the same size, colour and clarity, you must compare apples with apples. Things like make, fluorescence, girdle thickness must be considered. Some diamonds exhibit a cloudy or milky appearance. This is sometimes caused by an excessive amount of fluorescence but at other times this is in the crystal lattice of the stone and occurs in stones which have no fluorescence.
Cutters can make a stone look good on a certificate - paper pretty - by cutting only certain parameters to the acceptable limits, while cutting other less well-known angles and percentages to those completely outside those limits. By altering crown angles and star facet length, even the flattest crown could still have a 60 per cent table, and by increasing the girdle thickness and reducing the crown or pavilion depth, you could still have a stone of 60 per cent total depth.
People only know to look at certain things on a certificate - table depth, total depth and diameter; however, a clever cutter can still arrive at these with a badly-cut stone. A well-cut stone is made up of approximately 14 per cent crown, 3 per cent girdle and 43 per cent pavilion. A badly-cut stone with an 8 per cent crown and a 7 per cent girdle and 45 per cent pavilion still adds up to 60 per cent total depth. It could even have a 60 per cent table.
The diameter of a diamond can also give an indication of poor cutting. A well-cut carat stone measures 6.5mm. I have seen carat stones measuring 5.5mm. Prices of these stones are radically cheaper than better-cut stones of the same colour and clarity. These are not "paper pretty" stones, but often the lower the price, the less people look at the certificate.
With the growing number of internet sites selling diamonds, the public should be made more aware of the risks associated with this kind of purchase.
Even deals offering money-back guarantees can turn bad when the stone is finally seen and the buyer deems it to be not as good as he was expecting but the details appear to be substantiated by the certificate.
I am often asked for my opinion regarding certificate details in a prospective internet purchase. My answer is always the same: if the seller does not want to show you the stone prior to the purchase, do not go ahead with the sale. You look at the stone for the rest of you life, not the certificate.
The consumer is so price-driven these days that all they can see is that internet purchases are cheaper than retail. What they don't see are the multiple advantages of dealing with a retailer who can not only show them the stone, but advise them on the correct purchase. If you don't like the stone, they will get you another, regardless of whether the certificate says it is technically a good quality stone.
To complicate the issue a little further, the market includes not only blatantly wrong international certificates, but also "mistakes" made by reputable international certificate providers. These have been allowed to circulate and are accepted because they carry a name that normally does not attract criticism.
For example, an SI1 stone has been graded VS2 by mistake. Once the mistake has been noticed, this stone is not returned to the lab but sold for a price that reflects the true grading of the stone; however, the certificate remains unchanged, so the price of the stone looks like a bargain. If a stone like this is offered by an internet dealer, it is a sure-fire problem.
The internet is an amazing source of information. Potential diamond buyers quite rightly do their research on the net before making the purchase; however, it is often the case that they either stop reading before all the information is gathered or misunderstand the information presented.
For this reason it is up to all of us in the industry to make it a priority to educate those brave souls who deal directly with the public, so that they can then educate their diamond buying customers. This has the added advantage of creating a fifth "C": confidence - something the jewellery industry has been lacking in the recent past.
Name: Mike Muller
Business: Australian Diamond Grading Laboratory
Position: Partner
Years in industry: 26 years
Qualifications B.com GIA (diamonds)
Have "Your say": Login and add a comment below.