About diamond certificates

The purpose of a diamond certificate is to offer you the highest possible level of security and confidence. It confirms the diamond’s authenticity and describes its essential characteristics or ‘4 Cs’:

  • Carat
  • Colour
  • Clarity
  • Cut

Not just anyone can grade a diamond. It needs to be examined by expert gemmologists, under strict regulations and using specialised equipment. DGL Laboratorie’s host of in-house experts apply the most stringent grading conditions.

To ensure your absolute confidence, DGL Laboratory only grades polished diamonds that have not been set into a piece of jewellery.

DGL Laboratory believes that all customers need to be informed correctly about the diamonds they buy. That is why DGL Laboratorie’s Diamond Lab also examines whether a diamond has been subject to any unreported treatments in order to alter its appearance or whether it is synthetic, meaning that it was not born millions of years ago in nature, but in a laboratory.

The quality of a diamond is defined by means of the 4 Cs: carat, colour, clarity and cut. These four characteristics determine your stone’s value. And, as every diamond is unique, they are also very useful for identification.


The weight of a diamond is expressed in carats. One carat equals 0.2 grams or 100 points. Each diamond is weighed immediately upon receipt at the reception desk. DGL Laboratory has extremely accurate scales that measure up to 1/100,000 of a gram. This accurate weight is very useful for the identification of the diamond.


Most diamonds range in colour from white to slightly yellow. However, diamonds can occur in all sorts of colours ranging from brownish to striking yellow, pink, purple, red and blue. These are called ‘fancy colours’.


All diamonds have traces of their growth history. The clarity scale reflects the size, number, location and visibility of the internal characteristics when examined with a 10x loupe.


A diamond’s cut is essential to its beauty. If the diamond is not well-cut, the diamond will not interact with light as it should. Even a diamond with outstanding colour and clarity will not display the fire and brilliance that diamonds are famous for.

Since January 2010, DGL Laboratory has refined its cut grade, and now grades the diamond’s proportions, polish and symmetry. The polish describes the finish of the facets, while the proportions determine the brilliancy and the fire of the diamond. The symmetry describes the variations of the different parameters that define the proportions. Each grade is divided into 5 categories: Excellent, Very Good, Good, Fair and Poor.


A common misunderstanding is that the term ‘diamond cut’ would also refer to the diamond’s shape. However, cut is what determines how well-cut your diamond is, whereas shape is the shape it was cut into. Diamonds can be cut into various shapes of which the round brilliant is probably the best known.