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Colour 成色

Colour 成色

Most 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

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


一般人都以為鑽石透明無色,或只有白色。其實,大部分鑽石均略呈黃色或棕色,成色分級以距離透明無色的遠近為標準,顏色愈少,價值愈高。所以,說鑽石成色好,即代表無色。不過,彩色鑽石的價值衡量標準剛剛相反,顏色愈濃,價值愈高。

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。

GIA的成色尺度由D到Z,D為透明無色,而Z則是淺黃色或淺棕色,中間每一個字母代表了特定範圍的成色,那是一個區,而不是一個點。所以,如F色也可分為接近E色的較佳F色,以及接近G色的次佳F色,這有點像訂購演唱會門票,兩個人就是同樣用四百八十元買高價票,也可能出現一人坐最前排的座位,另一人卻坐在二百八十元中價票區的前一行呢。

在一般人眼中,E及F成色的裸鑽,看似無色。唯有富經驗的分級鑑定師,在合適的燈光環境下,再加上比色石輔助,經過客觀比對,才能確切地分辨。