150 Ashley Road, Hale,

Cheshire, WA15 9SA

0161 233 9977


Third Floor, St Johns Court, 19B Quay Street,

Manchester, M3 3HN

0800 080 3535


5 St Christopher’s Pl, Marylebone,

London, W1U 1NA

020 33 271 271

Book a Consultation
Pick A Location
Pick A Service
Pick A Date

Pick A Time


Confirm Details


Booking Enquiry Sent

We Will Be In Contact Soon!

Your booking Enquiry Information

Please Note: Your Booking is not confirmed until a member of our team sends you a confirmation email.

The Blog

Home The BlogWhy We Only Sell GIA Diamonds


Why We Only Sell GIA Diamonds

Why do Steven Stone only use GIA-certified diamonds?

Here at Steven Stone we only sell diamonds certified by the Gemological Institute of America (GIA) because they are the most stringent and respected diamond grading body in the world. Suppliers send their diamonds to be graded by experts in GIA laboratories who compare the diamonds to what are known as ‘master stones’. Their diamond experts assess each diamond based on the 4 ‘Cs’; cut, colour, clarity and carat weight.

Cut is determined from the average opinion of three experts and is arguably the most important as it affects your diamond’s sparkle! The colour ranges from D which is absolutely colourless to Z which has a strong yellow-brown colour. At Steven Stone we recommend choosing stones with colour above an H, this ensures your stone will look bright white to the naked eye. Clarity refers to the inclusions or imperfections that can be seen within the stone. A good quality diamond should be eye-clean meaning it has no visible inclusions when viewed with the naked eye. At Steven Stone we prefer to sell diamonds of SI1 (Small Inclusions) clarity and above. Carat weight is exactly that; the weight of the diamond. It is considered least important since stones of the same carat weight can look considerably different sizes depending on their measurements.

The 4Cs of diamond quality

Once graded, GIA produce a unique report or diamond dossier, for diamonds 0.15ct and upwards. This has a unique serial number which is also laser inscribed on the girdle of the stone itself and can be seen using 100 x magnification. The stones are then returned and diamonds from our trusted suppliers appear on our website listing.

What about other grading bodies?

There are several other reputable grading bodies which include the American Gem Society (AGS) and Diamond High Council (HRD). IGI and EGL have been known to inflate the grades of diamonds in several studies compared to the grading given by GIA meaning you, the customer, end up paying too much for a stone that is poorer in quality than stated on the certificate. Additionally when setting the diamond in a halo or shoulder-set engagement ring it may have a noticeable yellow or brown tinge which gives the game away that it is a lower colour than its certification states.

What do I need to know about in-house diamond certification?

Many larger high street jewellers do not use independent certification such as GIA to grade their diamonds. Instead, they opt to grade their diamonds in-house which can mean there is element of bias. This may result in poorer quality diamonds being graded much higher than if they were graded by GIA for instance. The most important thing about a diamond certificate is where it comes from. To be of any use, the diamond must be certified by an independent grading body and gem laboratory such as GIA, AGS and HRD. Independent certification exists to protect the consumer and to make sure you know exactly what you are buying!