diamond cut

  • Should you buy an engagement ring on the High Street?

  • Sapphire gemstone information

  • How to use a GIA inclusion plot to pick a beautiful diamond

  • How to choose your wedding ring

  • Emerald information

  • What is diamond strain?

  • How to clean your diamond jewellery

  • How to choose the perfect ruby

  • Asscher cut diamonds - a guide

    This style of diamond is often referred to as an Asscher cut diamond. In this light, we are looking to see which diamond has the brighter, whiter areas on the diamond and so which shows the best light return.

    The stone on the left is a typical square emerald. It is suffering from light leakage in the table of the diamond, making it a little glassy, which you can see by the lack of light return. The stone on the right is absolutely gorgeous with excellent light return. This is what you should be aiming for in Asscher cut diamond.

    It is apparent is the lack of fire in the table of the diamond on the left. This is caused by the facets not being correctly positioned causing light leakage in the stone. In comparison, the diamond on the right is looking absolutely stunning. This is also the amount of fire you should be aiming for stone cut to give the best optics.

    In terms of their proportions, both diamonds have a depth percentage of 68%. The table on the size right stone is 62% whilst the left hand stone is 58%. You might expect the stone with the smaller table to generate more fire from the crown, but as you can see this is not the case.

    This is why when we select our Asscher cut diamonds, we find it is essential to hand pick each one for perfect optics to ensure right level of brightness and fire in the diamond. This way we can weed out diamonds like the stone on the left, which sound rather good based on the information in the GIA lab report, but in practice disappoint when you inspect them with your eyes.

     

  • Princess cut diamonds - a guide

    When choosing a princess cut diamond, it is important to first assess the brilliance of the stone - this is the level of white light return and pattern of contrast generated by the diamond. Here is a comparison between one of our hand-picked, princess cut diamonds certified by GIA on the left, versus a typical GIA certified princess cut diamond on the right which didn’t pass our optical tests.

    The stone on the left has a very strong amount of white light return coupled with very nice pattern of contrast. The stone on the right has patches of good light return, but also has areas of light leakage which tend to give to give the diamond a grey overtone which looks less attractive to the naked eye.

    If you are researching buying a princess cut diamond, you will usually find suggestions on-line for the ideal table and depth percentages that the diamond should have. Both of these stones have a depth of 71% and a table of between a 71% and 72%. This is considered to be in a premium range and so accordingly you might expect both diamonds to be similar in terms of the amount of fire they create. However, they have very different levels of fire/refraction. This shows that it isn’t possible to reliably predict the optical performance of the diamond just from a GIA grading report or by comparing table and depth percentages.

    Another interesting observation is the size of the flashes of fire. Even though the stone on the right has less refraction, you will notice that the flashes of fire are a little larger in size than the diamond on the left. This is because it is a three chevron princess cut and hence has fewer facets on the pavilion. This doesn’t make the diamond more or less beautiful; it just changes the character of the stone a little.

    Next you can compare the sparkles of the diamond. The diamond on the left has a very good level of sparkle which is very attractive to the eye. In comparison, the diamond on the right has some areas of the stone which are really underperforming.

    Using the common dimensions of table and depth % as a guide to predict the optics of a princess cut diamond is very unreliable. The comparision shows that two stones which, according to the GIA report might suggest they are very similar, are in fact poles apart in terms of the appearance of the fire, scintillation and brilliance. This is why we hand pick every princess cut diamond.

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Samara James