There are many diamond grading laboratories around the world that offer varying degrees of diamond identification and grading services. There are many reputable laboratories that are world renowned for their strict grading criteria and consistency with their grading reports. At TOK Jewellers, we recommend purchasing natural diamonds that are accompanied by an independent grading report from the GIA (hyperlink) that also has its report number laser-inscribed on the girdle of the diamond – this gives buyers the certainty and peace of mind when making such a large purchase.
GIA is world leader in diamond research, grading and consistency with their processes. They are the most highly regarded laboratory around the world by the diamond industry. Other reputable diamond grading laboratories that we recommend are: AGS, GSL, IGI, HRD and DCLA.
Along with the overall cut-grade of a diamond, it is also very important to ensure that a diamonds final polish and facet arrangement (symmetry) are of high standards. If the diamond does not have a high polish and has lop-sided facets, it results in the diamond looking dull and can cause windows/dark spots on the surface of the diamond, which makes them look very unappealing and reduces their light performance. Polish and Symmetry are graded as being from EXCELLENT, VERY GOOD, GOOD, FAIR or POOR. At Tok Jewellers, we stock and sell GIA-certified diamonds with polish and symmetry grades of EXCELLENT and VERY GOOD as they represent the best quality diamonds.
This is where our extensive knowledge and supplier network can assess the diamond by hand and determine if the fluorescence is positive or negative, thus ensuring that you make a worthy purchase. The presence of fluoresce can significantly affect a diamonds price, especially if the reaction is negative.
At Tok Jewellers, we recommend that if a diamond has a Medium, Strong or Very Strong fluorescence grade, it should be inspected before purchasing to ensure that the fluorescence is positive. Diamonds with no or faint fluorescence can be purchased without hesitation, provided all other quality factors are ideal.
Due to the environment in which natural diamonds are formed, it is very common for them to have a tinge/body colour that can affect their appearance and ultimately, their price. The most common colour of tinges/body colour are brown and green, and when present they can really diminish the look and appeal of a diamond.
More and more diamonds are being treated to enhance their colour and clarity, and there are many undetected man-made diamonds that have infiltrated the marketplace. Many of these treatments and synthetics are undetectable to most people and many retailers are not disclosing these types of diamonds when selling them.
Some of the different types of treatments that can be undertaken on a diamond are:
- Fracture-Filling/Laser-Drilling: this is where a heavily included diamond is penetrated by a laser that blasts away the heavy inclusions in the diamond and fills the resulting cavity with a glass/silicon filling solution. These diamonds frequently display a red/purple “flash effect”. The critical thing to remember with these diamonds is that the treatment is not permanent and is known to reverse when exposed to jewellery repair work (re-sizing, cleaning etc.), heavy knocking or even air-travel has been known to cause the treatments to reverse; which results in the appearance of the diamond being cloudy, black or hazy.
this is where a diamond is treated by extreme heat and pressure in order to enhance its colour. This is a relatively harmless and stable treatment, but it can significantly reduce a diamonds value.
- Synthetics: these are diamonds that have not been formed by nature, rather, they have been grown in a laboratory. They have near identical properties to natural diamonds and cannot be easily detected by most customers.