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Colour 成色

Diamond colour scaleMost people think that diamond is colourless, or is only white in colour. In fact, most diamonds have traces of light yellow or brown. When grading the colour of a diamond, the scale begins with the highest rating for colourless diamonds. The whiter or more “colourless” a diamond is, the higher its value. Therefore, when we say a diamond has got a good colour, we actually mean it is colourless. However, the grading of fancy colour diamonds is on a reverse scale, i.e. the more saturated the colour, the higher its value.

Since the late 1950s, the grading standard for the colour of a diamond created by the Gemological Institute of America (GIA) was widely adopted by the diamond industry around the world. The quality assessment report by GIA Laboratory is a widely recognised industry standard. The certificate we receive today when buying a diamond is most likely a GIA one.

GIA's professional colour scale begins with the highest rating of D for colourless diamonds, and continues all the way to Z for diamonds with traces of very light yellow or brown. Every alphabet represents a range, not a point. Hence, grade F colour can be considered a better grade F when its colour is close to grade E colour, or an inferior grade F when its colour is close to grade G. This is somewhat like ordering concert tickets: Even though two people may both have purchased HK$480 tickets, one may be allocated to a front-row seat in the price zone while another may get a back-row seat that is right in front of the zone area of HK$280.

Loose diamonds graded E and F are virtually colourless, to an amateur. Only experienced grade appraisers, in the right lighting conditions and through objective comparison with the master stone, can truly tell how colourless the diamonds are.

用來比較鑽石成色的比色石 Master stones are used in the diamond-grading process
Master stones are used in the diamond-grading process


GIA(美國寶石學院)所訂下的鑽石成色分級標準,在1950年代末期之後,廣為世界鑽石業所採用。而GIA之寶石鑑定中心GIA Laboratory的品質分析報告書,就成為業內普遍的標準,認受性非常高。現今我們購買鑽石時所附有的證書,亦多是這一種。