Colour Characteristics of Blue Sapphire from Madagascar

In order to investigate the colour characteristics of the blue sapphire from Madagascar, the GemDialogue systerm is used for describing and grading the blue sapphire samples.Comparing with the sapphire samples from Australia, Sri Lanka, Kampuchea and Burma, the colour characteristics of the blue sapphire samples from Madagascar are blue with a little high black colour mask, in the range of 1~4 colour grade, which belong to the comercial grade.In order to determine the relationship between its colour and the contents of total Fe and Ti, UV-VIS spectrophotometer and electro microprobe are used to analyse the samples.The results show that the blue colour of the sapphire sample changes to darker as the contents of total Fe and Ti increase.The blue colour of the sapphire sample is more pure as the content of total Fe is 0.02%~0.75%, the content of Ti is 0.006%~0.040% and the content ratio of total Fe to Ti is 10~30.When more than these ranges, the colour of the sapphire sample is usually green or purple hue.