SSEF and Gübelin Harmonize ‘Pigeon Blood Red’ and ‘Royal blue’ StandardsNovember 08, 15
(IDEX Online News) – Swiss-based Gübelin Gem Lab and the Swiss Gemmological Institute SSEF have standardized the usage of the “pigeon blood red” and “royal blue” for describing rubies and sapphires, respectively in an attempt to bring uniformity to the gemstone grading industry.
Up until now, there has not been a definite agreement as to the exact color and quality criteria that correspond to the two terms, leading to “inflationary” and frequently ambiguous usage on lab reports.
For either type of gemstone to receive either a pigeon blood red or royal blue classification, the color has to be an “intense, saturated and homogeneous red or blue.”
“Pigeon blood red” is best described as a red color, with no apparent color modifiers (such as blue or brown). A minute purplish tint is acceptable. The body color of pigeon blood red rubies is complemented by a strong fluorescence when exposed to ultraviolet light. This fluorescence is caused by high chromium content combined with low iron content, and results in the distinct "inner glow" coveted by ruby connoisseurs.
“Royal blue” is best described as a saturated blue color, either pure or with a very slight purplish tint. While “royal blue” is a term that was historically coined for the best quality of sapphires originating from the Mogok area in Burma, sapphires from other metamorphic deposits, such as those found in Madagascar and Sri Lanka, may also display the properties required to qualify for the term.
In terms of quality, these color terms can only be applied to rubies and sapphires that exhibit fine qualities and have not undergone any modification of color and/or clarity. Any type of treatment disqualifies them from being described using these color terms. Furthermore, they must be relatively free of eye-visible or dark inclusions, and they must show a homogeneous color distribution with vivid internal reflections.