It is very important to ask for a certified diamond that has been assessed and graded by an independent gemological laboratory with certificates universally recognised. Certificates issued by GIA (Gemological Institute of America) are the most internationally recognised. Other popular laboratories are IGI, IGL, EGL, HRD, DCLA and others. At Joseph George Jewellery, all diamonds over 0.30ct are GIA certified.
Cut grade, Symmetry, Polish are graded with Excellent (EX), Very Good (VG) and Good (G). Always prefer EX and VG with preference EX. The difference is indistinguishable to an untrained eye but you will see that an EX EX EX stone has more brilliance and life than a VG VG VG, when put next to each other.
Colour D – to – H are all white with a very slight difference from one colour to the next. When the diamond is colourless, the light that reflect from the facets, breaks evenly in to all the spectrum of colours. When a diamond has a yellowish tint, this colour overpowers all the other colours with the result it not being as dazzling and colourful.
Clarity IF to SI2 are eye-clean when GIA certified, especially the multi-faceted cuts like the round, princess and cushion. For best value, if you do not want to pay for something you cannot see, try to stay within the SI1 – SI2 clarity. An exception are the emerald and baguette cut diamonds for which you need a clarity VS or above, because of the larger and fewer facets.
Fluorescence is graded with Non (N), Slight (SL), Medium (M) and Fluorescence (F). Under incandescent light, a stone with fluorescence has a strong violet-blue colour which overpowers all the other colours of the light spectrum. It is best to have None or Slight.
Fancy colour diamonds are another popular choice. These diamonds are with strong hues like yellow, Champaign, cognac, blue, pink and red.