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PIGEON BLOOD
Ruby
Provenance
Pigeon blood ruby is traditionally used to describe the finest colours of Burmese (Myanmar) ruby. The Burmese legend of the first ruby in the Mogok Valley describes it as having been mistaken for the purest blood by a magical being. The legend is described in Jesseph Kessel's "Valley of the Rubies" as follows:
"A huge piece of fresh flesh was shining on the side of a hill. And this flesh was of such quality that the old eagle, who had hunted so long above the boundless world, had never seen it before. It was the colour of the brightest, purest, sweetest blood. And all the light of the day seemed made for it, so sparkling was it. [...] It was not a piece of meat that glistened in the grass of the hill, but a miraculous and sacred stone, a stone like no other, made of the fire and blood of the earth. [...] This stone was the first ruby in the world."
This legend goes back at least to the Middle Ages, the earliest mention known to us of Pigeon blood is the story of the famous royal ruby or Nga Mauk ruby described as being of the colour of pigeon's blood.
Another legend mentions that Burmese warriors in medieval times put rubies in contact with their blood to gain invulnerability in battle. The ancient Greeks believed that rubies were a remnant of a god's blood.
Red has always been associated with blood, sacrifice and courage. Modern studies in Europe and the United States show that red is the colour most associated with heat, passion, sexuality, love and joy. In China, India and many Asian countries, red is the colour that symbolises happiness and good fortune.
It is therefore not surprising that pigeon's blood, which most probably recalls the red colour of a pigeon's fresh blood or the blood-red ring surrounding a pigeon's eyes, became the historical adjective describing the best red, first by the Burmese and then by the traders along the Silk Road. It may have been the best red they could find at the time, or it may be a poetic term reminiscent of a long lost Burmese legend.
Definition
Colour has the greatest influence on the value of a ruby. Pigeon's blood describes rubies with a pure red to very slightly purplish red hue, with a vivid saturation, which can in rare cases range from intense to deep, the tones should be medium to medium dark. For more information on colour classification, see here.
Fluorescence of pigeon's blood rubies in the long-wave ultraviolet (365 nm) is preferably strong to medium, with some rare cases of faint red. The almost magical " glowing " red produced by the ruby's absorption of the sun's ultraviolet light to produce an additional layer of pure red (699 nm) adds an important component to its colour. It is therefore not surprising that many of the rubies we may call "pigeon's blood" come from low iron rubies with very strong red fluorescence, such as Burma (Myanmar) with Mogok and Mong Hsu, and Vietnam with Luc Yen. However, mafic-ultramafic rubies, such as those from Mozambique and Madagascar, with low to medium iron content, can also show spectacular fluorescence, thus fulfilling all the colour requirements to be called "pigeon's blood".
Clarity has a very important influence on the value of a ruby. Pigeon's blood ruby must be flawless, preferably clean to the eye, or at least transparent, without pronounced inclusions that are very visible under the table. The colour uniformity must be excellent or evenly distributed.
Cut plays a very important role in the colour of a ruby. Pigeon blood rubies should have excellent to good proportions to maximise total internal reflection. Pigeon blood rubies should not show significant windowing (transparent area) and/or extinction when viewed face up.
Treatment of pigeon blood rubies is acceptable only for no treatment or traditional heating. Therefore, any other treatment such as diffusion of foreign ions into the ruby lattice, such as beryllium, fracture sealing with resin, or lead and silicate glass, will not be granted a gemmological report and as such not qualified for Pigeon blood or any other colour grading.
Pigeon blood ruby fluorescence and under daylight illumination. Reference collection Bellerophon Gemlab.
Science
The classification of the colour of a gemstone is both an art and a science. The adjective "pigeon's blood" combines many facts about a ruby. Classifying the colour of a transparent anisotropic material is not as simple as it sounds. The hue, saturation and tones must fall within a predetermined range for the ruby to be considered "pigeon blood".
The red colour of rubies is the result of a major chromophore: chromium. It replaces some of the aluminium atoms in the structure, the more chromium, the redder the ruby, and the stronger the fluorescence, this is true up to a point, too much and the ruby will be dark to almost black, and the fluorescence will be greatly reduced. The approximate chromium content in most rubies is between 0.1 and 4%. Two other chromophores almost always play a role in ruby: iron and titanium (Fe3+ alone and/or Fe+3 in pairs, and Fe2+ in pairs with Ti4+). The iron content tends to make the ruby orange, decreasing the red saturation and increasing its tone as well as killing the fluorescence, while titanium (in pairs with iron) makes the ruby purplish.
Quantifying the chromophores present in a ruby provides a good starting point for colour comparison without the influence of other factors such as the path of light through the stone and reflections. By combining this method with natural long-wave ultraviolet spectrophotometry to correctly quantify the fluorescence present, as well as the overall proportions of the stone, we can analyse the most influential colour factors separately and compare them to our reference collection of "pigeon's blood" rubies.
It should be noted that although most of the data analysed when classifying the colour of a ruby is empirical, the combination of interpretations of this data for a pigeon's blood ruby is in the realm of comparative analysis.
To add to the complexity, a ruby can also behave very differently depending on the lighting conditions created by different geographical locations around the world.
In conclusion, rubies that can be called "pigeon's blood" basically describe the most vivid colour with the incorporation of clarity, fluorescence, proportions and treatments prerequisite.
Pigeon Blood Criteria
Hue
Tone
Saturation
Fluorescence
Clarity
Homogeneity
Total Internal Reflection
Treatment
Red to very slightly purplish red
Medium to medium dark
Intense to vivid
Medium to strong
Flawless to transparent
Excellent to very good
Excellent to very good (>70%)
None or traditional heating
