The four C’s
When determining the quality of a diamond we refer to the 4 c’s. Detailed below is a description of each of these factors of quality. At Jewellery Watch Repairs and Restoration London we only deal with diamonds that are a minimum of commercial quality, and usually higher. Our larger diamonds are often certificated, so you can be precisely sure of the type of diamond you are receiving as a diamond replacement for jewellery when needs repairs.
The cut of a diamond speaks of its proportions. A well cut diamond will have a greater brilliance than a diamond that is cut poorly. This is due to the angles caused by the internal refraction from the diamond facets.
Illustrated is a round brilliant cut diamond. You can see from the diagram that when the diamond is cut either too shallow or too deep, the light is unable to exit in the correct fashion and therefore results in a duller diamond.
There are various other types of cut of diamond, such as emerald cut, marquise and princess (square shape).
Colour is of great importance when determining the quality of a diamond. To the untrained eye, most colours from D to N appear as white. Though upon closer inspection under proper lighting, there are significant differences in this range. The most prescious and valuable diamonds are those that are colourless.
The illustration gives an idea of the grading scale used to grade the colour of diamonds, which range from D (completely colourless) to Z (brown).
The clarity of a diamond means in fact “the purity” of the diamond. When diamond is excavated it contains traces of other rocks. These are dark materials that vary in size, and can dramatically affect the appearance of a diamond. They are sometimes called ‘nature’s fingerprints’. Diamonds that have few and small inclusions are more valuable than those are highly included. The placement of the inclusions is also of importance. An inclusion in the centre of the diamond is considered to be of greater detriment to the quality and value than if is near the girdle.
The following diagram gives examples of clarity at the various grades. Generally, the inclusions in diamonds from F to SI are mostly unnoticeable to the untrained eye.
The most obvious factor. The ‘carat’ weight of a diamond determines its mass, and therefore its size. This picture is a jewellery scale giving an example of diamond scale. 1 carat weight 0.2g.
What is a diamond certificate?
A diamond certificate is a report issued by an independent gem laboratory which fully describes the diamond. Expert gemmologists analyse and record the colour, clarity, cut and carat weight, as well as the precise dimensions of the diamond. Some of them ilustrate the diamond showing inclusions.
A diamond certificate is your assurance that you are getting exactly the same diamond as described, and to ensure that you are getting value for money for your diamond. Other retailers may offer large uncertificated diamonds, where the specified quality of the diamond is often estimated by the salespeople, leaving a margin for error. A certificate from an independent laboratory such as GIA, is conclusive evidence of the quality of the diamond, and therefore allows you to buy with confidence that you are getting a quality product. It is also useful for insuring the diamond. A diamond certificate is proof to your insurance company of the quality and size of the diamond.
However not all diamond certificates are created equal. Unless they are issued by a reputable laboratory, be wary. This is why Jewellery Watch Repairs and Restoration uses mainly GIA which stands for Gemological Institute of America.
Do I need a diamond certificate? How to choose a diamond replacement?
A certificate is not needed for all diamonds. In general, a diamond certificate is not necessary unless you are purchasing a particularly expensive diamond, e.g. half carat and above. If you need a diamond replacement for your ring or pendant, then you might not needs a diamond certificate.Certificated diamonds also allow you to compare prices from one online shop to another.