Adiamond that has been certificated by an independent laboratory is your guarantee of the quality and characteristics of the diamond you choose. The diamond report confirms: the stone is a natural diamond carat weight colour clarity cut It will also give other properties such as measurements, and if the gem is fluorescent under long wave ultra-violet light. If strong fluorescence is noted, this may result in a minor reduction in the value of the stone, although the property of slight fluorescence generally does not affect either the quality or the value. When buying certificated diamonds, the report should come from a reputable, internationally recognised laboratory such as the GIA (Gemmological Institute of America), or IGI (International Gemmological Institute). These organisations are totally independent, as they are not involved in buying, selling or valuation of gems. A certificate from an expert grading laboratory will enable a reputable jeweller to give you a market value for your diamond without even seeing the stone, as there is an international pricing structure for certified diamonds.