Pigeon Blood — The Trade Term for the Finest Ruby Colour
Pigeon Blood — The Trade Term for the Finest Ruby Colour
A laboratory designation that adds materially to value but lacks a single scientific definition
Pigeon blood is the trade term for the finest grade of ruby colour: a pure red to slightly purplish red of vivid saturation, medium tone, and characteristically strong red fluorescence under long-wave ultraviolet light. The phrase is reserved by convention for stones that meet a high standard, and its presence on a laboratory report typically increases market value by 20 to 60 per cent over an otherwise comparable ruby that fails to attain the designation. Despite the term's commercial weight, it lacks a single agreed scientific definition, and the criteria differ across the laboratories that issue it.
Origin of the term
The term has been used in the Burmese trade since at least the late nineteenth century, where Mogok dealers compared the finest material to the colour of a freshly killed pigeon, or to the first two drops of blood drawn from the nostril of a live pigeon — descriptions which appear in nineteenth-century gemmological accounts and continue to circulate in the trade. The term is not derived from any scientific reference and is not standardised across the literature. Translations into Burmese (ko-twe) and into trade languages elsewhere in Southeast Asia carry the same connotation but rarely attempt a precise colour specification.
Laboratory designation
Several laboratories now issue formal pigeon-blood designations on their reports. Lotus Gemology in Bangkok publishes detailed criteria covering hue, saturation, tone, and fluorescence, with the designation reserved for stones meeting all four criteria simultaneously. GRS issues its own variant of the designation, with sub-grades that have been the subject of trade discussion. Gübelin Gem Lab and AGL also issue the designation under their respective protocols, and SSEF in Basel uses related but distinct language for stones of comparable quality.
The criteria are similar in intent but not identical, and a stone may attain the designation at one laboratory and not at another. Trade practice is to commission reports from the laboratory whose designation will carry most weight in the destination market — Gübelin and SSEF for European auction, GRS or Lotus for the Asian trade, AGL for the American market.
The designation is reserved for stones of natural origin and conventional heat treatment only; rubies treated by lead-glass filling, beryllium diffusion, or other aggressive methods are excluded regardless of apparent colour. Unheated stones attain the designation more readily and command a further premium over heated stones at the same colour level.
Origin association
Pigeon-blood colour is most strongly associated with Mogok, Burma, where the marble-hosted geological setting produces rubies with high chromium and unusually low iron, the combination responsible for both the saturated red colour and the strong fluorescence. The traditional trade understanding of pigeon blood is in fact tied to this Mogok signature, and some laboratories continue to associate the designation principally with Burmese material.
Mozambican rubies from the Montepuez deposit, in the right colour range, also attain pigeon-blood designations from the laboratories that recognise non-Burmese sources for the term. Vietnamese rubies from Luc Yen and the now-largely-exhausted Mong Hsu deposit have similarly been designated where colour and fluorescence support the call. The relationship between origin and the designation has been the subject of considerable trade debate, and the practice of separating colour designation from origin opinion is now standard at the major laboratories.
Practical implications
For a buyer or seller, the practical question is whether to commission a pigeon-blood report on a given stone. The designation adds materially to value, but the laboratories will only issue it where the stone clearly meets the criteria — submitting marginal material is an expensive way to confirm that a stone falls just short. For stones of likely passing quality and significant value, the report is essential; for borderline stones, a preliminary opinion from a knowledgeable trade contact often saves the commissioning fee.