One of the greatest challenges gem dealers and gemologists face today is being able to accurately determine if a stone has been heat treated. While a 100% reliable answer to that question is a job for a major gem lab, there is a simple and inexpensive tool that can often give an important indication.
So what is this miracle tool? We speak of the lowly ultraviolet light.
It wasn’t long ago that ultraviolet (UV) fluorescence was considered the poor stepchild of the gem lab, a pint-sized pea shooter when compared with the high-caliber cannons available in modern labs. But with the rising importance of treatment detection, the humble UV lamp is making a comeback.
Many heat-treated rubies and sapphires will display chalky short-wave (SW) fluorescence. This reaction is practically never found in untreated corundums and was first noted by Robert Crowningshield (1966, 1970). It is actually the colorless portions of the stone that fluoresce (a reaction similar to Verneuil synthetic sapphires). Since colorless areas follow the original crystal’s growth structure, the fluorescence will follow the same pattern as the gem’s color zoning. In addition, other trace elements in corundum may produce fluorescent reactions, from the well-known red glow of ruby to other reactions that are still not completely understood. Many will be illustrated below, both known and unknown.
Show and tell.
So how does one go about checking for this reaction? The first step is to obtain a combination LW/SW lamp. You will also need a pair of protective glasses (SW light can burn your eyes with prolonged exposure). A viewing cabinet is also a plus. Finally, you will need a small lens to magnify the stone. Figures 6 –8 show one setup for both viewing and photographing fluorescence.
When observing fluorescence, the idea is to hold the stone with tweezers and bring it as close as possible to the lamp and view it under magnification. Examine the stone from all angles; many times the key chalky areas are confined to tiny portions of the stone.
One of the authors (Hughes, 1997) has suggested a lens be incorporated as an integral part of the viewing cabinet, but sadly instrument manufacturers have yet to produce such a unit.
This test does require a bit of knowledge. If a ruby or sapphire shows a chalky fluorescence in SW, it is probably heat treated. If it is inert, that does not mean it’s unheated. Also be careful that the stone is clean. Soap and other chemicals can also produce chalky fluorescence. And while this test is a tool that can be extremely useful, it is not a substitute for a complete gemological examination in a fully-equipped laboratory. Finally, keep the exposure times of corundum to SW fluorescence to a minimum. SW irradiation does create a yellow color center that can alter the color of the gem; even five minutes exposure can do this (see Figure 9). While this color fades with prolonged exposure to daylight, it can turn a blue stone more greenish (not good if it’s your stone and you’re trying to sell it).
Breaking down fluorescence.
In its most basic sense, fluorescence is the emission of visible energy of a longer wavelength when bombarded by energy of a shorterwavelength. The stimulating energy may be x-rays (x-ray fluorescence), ultraviolet light (UV fluorescence) or even visible light. Ruby provides an excellent example of the latter.
When a ruby is put into daylight, certain electrons are excited to higher orbitals, producing absorption of the corresponding wavelengths. But instead of falling straight back to the ground state, the electrons fall in steps. In most cases, the release of energy from each of those steps is in the form of phonons to the crystal lattice (vibrational heat), and thus invisible to the human eye. But in the case of ruby, some emissions fall into the red (at 692.8 and 694.2 nm). This is what makes ruby so special; not only does it possess a red body color, but that red body color is supercharged by red fluorescence. This is what led the ancients to believe ruby had a fire burning inside.
UV fluorescence can be an extremely sensitive indicator not only of trace impurities, but also the conditions under which the gem formed. Indeed, it is not unusual for fluorescence to be easily seen from strongly-fluorescing ions at concentrations in the range of 0.01 parts-per-million (ppm). For lay people, that’s an itsy-bitsy amount, completely beyond the detection limits of all but the most sophisticated and expensive analytical equipment.
Speaking of sapphire.
While the red fluorescence of ruby is detailed in many gemological texts (c.f. Hughes, 1997), the cause of the chalky fluorescence has not been covered. Let’s take a look at it.
Sapphire generally shows no fluorescence to visible light. But that changes if we expose it to short-wave UV. This is most clearly seen in synthetic colorless sapphire, which displays a bluish white (‘chalky’) emission in the range of 410–420 nm.
This blue fluorescence in synthetic sapphire has been observed at least since 1948. While it has been generally ignored in the gemological literature, it has been the subject of numerous scientific papers (c.f. Evans, 1994).
Evans surmised after reviewing the data that the 410–420 nm fluorescent peak was due to Ti4+ charge-transfer transition. That was later confirmed by Wong, et al. (1995a and 1995b). Isolated Ti4+ ions, or Ti–Al vacancy pairs produce this fluorescence.
The Ti4+ charge-transfer transition in corundum is so strong and the efficiency so high that the fluorescence is easily observed by eye at even just 1 ppm Ti4+. Most of the synthetic sapphire in the market contains at least one ppm of Ti4+ from the Al2O3 starting material, if not more, and thus fluoresces. The fluorescence peaks at about 415 nm at very low Ti4+ concentrations, but as the concentration increases, the fluorescent band broadens and the peak shifts to as high as 460 or 480 nm, making the fluorescence appear more greenish-blue or whitish-blue.
Why this chalky fluorescence occurs relates to the growth temperature and Ti4+ concentrations relative to other impurities. In synthetic corundums, the high growth temperatures and high Ti4+ concentrations produce the chalky fluorescence. In certain heat-treated sapphires with low Fe levels (such as those from Sri Lanka), high-temperature heat treatment creates similar conditions to the synthetic. Thus the chalky fluorescence.
But what about natural, untreated sapphires? Why don’t they fluoresce blue or bluish white? The reason relates to growth temperatures and time. Natural sapphires grow at much lower temperatures, so Ti4+ is much less likely to pair up with Al vacancies.
These lower temperatures also allow easier pairing of Ti4+ with other ions (usually Fe2+ or Mg2+) that prevent fluorescence. Another damper is the presence of Fe3+, which also kills fluorescence. And finally, as the crystal sits in the ground for millions of years, diffusion slowly takes place, allowing the Ti4+ to slowly pair up with other ions, thus killing the fluorescence.
Why then, do some heat-treated blue sapphires fluoresce chalky blue to green or white, and what causes the difference in appearance?
When blue (or geuda) sapphires are found in nature, they usually contain exsolved rutile. Titanium is concentrated in these rutile micro-crystals. When the stone is heat treated, the rutile dissolves into the corundum by diffusion, but because diffusion is slow, the local concentration of Ti4+ can be quite high. In the high concentration regions the Ti4+ concentration will exceed the local charge compensators (Fe2+ or Mg2+) and thus free Ti4+ ions will form. In addition, the dissolution of rutile will locally force the creation of some aluminum vacancies and some of the Ti4+–Al vacancy clusters will form. These types will fluoresce and thus some heat-treated sapphire will fluoresce somewhat like synthetic Ti-bearing sapphire. Because the original distribution of rutile (and iron in solution) occurred in zones, the distribution of the fluorescence will reflect that zoning. The fluorescence will be most intense where Fe is lowest and Ti4+ is highest, i.e. in areas of minimal color. The high iron-content basaltic sapphire (such as that from Australia, Thailand, etc.) will not fluoresce after heat treatment, as the iron concentration is much higher than the Ti4+ concentration everywhere.
The appearance of chalky fluorescence in a corundum depends strongly on both the Ti4+ and Fe3+ concentrations. Considering Ti4+first, it is important to note that the charge-transfer absorption in the UV per ion is extremely high. If we look at the fluorescence of a piece of synthetic sapphire with several ppm of Ti4+, it seems to glow blue throughout the volume. This is because the total Ti4+charge-transfer absorption is low enough that the UV photons can penetrate into the bulk of the sample. When the Ti4+ concentration is higher, the fluorescence seems to be coming from a thick layer near the surface because that is as far as the UV photons can penetrate. At high Ti4+ concentrations, only a thin surface layer is penetrated by the UV and the fluorescence appears as a chalky surface layer (see Figures 15 & 16). The charge transfer absorption of Fe3+ is also very high. Thus iron will contribute to limiting the penetration of UV into the sample also. Thus the very different appearance of the fluorescence of some synthetic sapphire and some heat-treated natural sapphire is not a different phenomenon, just a difference in impurity concentration.
One of the authors (JLE) has used a Schott BG-12 filter to heighten the superficial chalky fluorescence often seen in heat-treated ruby. This filter eliminates the red fluorescence and transmits the Ti4+ blue fluorescence (Figure 17).
The traditional gemological versus the laser junkie.
While laser junkies focus strongly on the subject of fluorescence of ions in crystals, it is an orphaned topic in gemology. Let’s look at the different approaches.
With gemology, fluorescence is typically only visually observed with either LW or SW UV radiation, with the results recorded in terms of just brightness, color, and the presence or absence of phosphorescence.
In the study of ions in crystals, the parameters measured are more extensive. Typically the spectral distribution of the fluorescence is measured, as well as the spectral distribution of the light that can excite that fluorescence (excitation spectrum). In addition, the temporal decay parameters of the fluorescence are measured using a short pulse light source. Sometimes the decay curve is a single exponential indicating a single site or a single ion. Other times the decay curve is a combination of two or more exponentials indicating multiple sites or multiple ions. All of these parameters are often measured as a function of temperature.
With UV fluorescence, we have something all too rare in gemology today: an inexpensive test that is as sensitive as even bomb-science level analytical equipment.
Now what does this mean for a gem dealer? With a small UV lamp, one can quickly check potential purchases. Any stones that show a chalky SW fluorescence are most likely heat treated. Total equipment outlay? The lamp alone costs less than $300. Heh, heh, heh, we can already see you smiling.
And for the laboratory gemologist? This technique has been under-appreciated in the gemological community. Fluorescence might provide an avenue to determine if some sapphires have received heat treatment at temperatures lower than those normally used for geuda. But this will require adopting some of the techniques and instrumentation of the laser junkie. While expenditures for such instrumentation are hard to justify without a guarantee of just what may be learned, the increasing need to stay abreast of gemstone treatments requires an expansion of our array of techniques. Sophisticated fluorescence instrumentation is far less expensive than SIMS, LA-ICP-MS or LIBS analysis. Perhaps not quite so sexy (nor nearly as expensive), but when it comes to utility, this still looks like a pretty decent dance partner.
Figure 18 - The myth of purity. Crystals arise not from an ideal source, but spread out from a mixed broth. As they grow, the composition of that nectar changes because each influences the other. Diffusion is always a two-way street. The above photo is a map-like microcosm of this concept. Compositional areas lie tightly bounded in places, while blurred in others. The notion that either terrestrial or biologic creations might be “pure” is a myth. All are products of the past, all are affected by the present, all will be affected by the environment in which they reside, while simultaneously affecting that environment themselves. Each of these conditions is unique to the individual, as the above image shows. Thus no two will ever be alike. Heat-treated blue sapphire in SW UV. Photo: Richard W. Hughes; Nikon D200.
Crowningshield, R. (1966) Developments and Highlights at the Gem Trade Lab in New York: Unusual items encountered [sapphire with unusual fluorescence]. Gems and Gemology, Vol. 12, No. 3, Fall, p. 73.
Crowningshield, R. (1970) Developments and Highlights at GIA’s Lab in New York: Unusual fluorescence. Gems and Gemology, Vol. 13, No. 4, Winter, pp. 120–122.
Evans, B.D. (1994) Ubiquitous blue luminescence from undoped synthetic sapphire. Journal of Luminescence, Vol. 60–61, pp. 620–626.
Hoover, D.B. and Theisen, A.F. (1993) Fluorescence excitation-emission spectra of chromium-containing gems: An explanation for the effectiveness of the crossed filter method. Australian Gemmologist, Vol. 18, No. 6, May, pp. 182–187.
Hughes, R.W. (1997) Ruby & Sapphire. Boulder, CO, RWH Publishing, 512 pp.
Robbins, M. (1994) Fluorescence: Gems and Minerals Under Ultraviolet Light. Phoenix, AZ, Geoscience Press, 374 pp.
Wong, W.C., McClure, D.C. et al. (1995b) Charge-exchange processes in titanium-doped sapphire crystals. I. Charge-exchange energies and titanium-bound exitons. Physical Review B, Vol. 61, No. 9, pp. 5682–5692.
Wong, W.C., McClure, D.C. et al. (1995a) Charge-exchange processes in titanium-doped sapphire crystals. II. Charge-transfer transition states, carrier trapping, and detrapping. Physical Review B, Vol. 61, No. 9, pp. 5693–5698.
RWH wishes to thank John I. Koivula for his encouragement and suggestions during the writing of this article.
About the authors.
Richard Hughes is the author of the classic Ruby & Sapphire and over 100 articles on various aspects of gemology. His writings can be found on his personal web site, www.ruby-sapphire.com.
Dr. John Emmett is one of the world’s foremost authorities on the heat treatment, physics, chemistry and crystallography of corundum. He is a former associate director of Lawrence Livermore National Laboratory and a co-founder of Crystal Chemistry, which is involved with heat treatment of gemstones.
This article came about following RWH’s plunge back into serious gemology in January 2005, when he joined the AGTA GTC. While checking the SW fluorescence of a heated sapphire, he decided to call JLE to inquire about the cause of the chalky fluorescence in heated and synthetic sapphires. “Interesting that you should ask,” Emmett replied. “I’ve been doing much thinking about that same subject of late.” And so it was that RWH and JLE began sharing thoughts on this subject.
Penned in bits and pieces in the first half of 2005, an edited version appeared in The Guide (Sept.–Oct. 2005, Vol. 24, Issue 5, Part 1, pp. 1, 4–7. Pieces also appeared as part of the AGTA GTC’s regular Laboratory Updates.
Read the original article on http://www.ruby-sapphire.com/heat_seeker_uv_fluorescence.htm
Paolo Minieri, President of Gemtech
Not long ago they did not like the name pigeon blood.
The combination of ruby and blood is lost in the mists of time. References are found in the Chinese reports and in Arabic (the great medieval gemologist At-Tifasci and Al Afghani dealt with the subject). But tallying ruby to pigeons’ blood has more controversial origins. In all likelihood the vividness of the attribute (in Burmese ko-twe) stems more from a tint of the pigeon's eye than from its blood. The expression was then taken up again when in the second half of the nineteenth century the precious material came into the hands of the incredulous British officers. Yet, with absolute certainty, the dispute over the relevancy of such definition rages from the month of October 2015. The scope of this dispute is a global one; yet it is consumed entirely in Switzerland, a small country as for extension, however decisive as for gemological authority. Let's take a step back. In the last century, the historical process that gradually led to the currently used gemological classification standards is characterized, moreover, by the progressive tendency to avoid the descriptive nomenclature, using instead references to quantitative parameters.
Take for example the color of diamonds. To detect the deviation from white, grades expressed in alphabetical letters have been adopted. This system must have seemed absolutely more objective than the one linked to mining places. Similarly, parameters based on tint, tone and saturation have been adopted to regulate the color classification of other gemstones. As far as ruby is concerned, the best combination between tone, body color and high saturation is generally indicated as vivid red. This is the color grade connoting the most coveted gems and this is the context in which ruby lovers have placed the pigeon blood.
Yet for decades the definition pigeon blood has not been used in the reports, being, to the eyes of the specialists, a sort of subjective description, a metaphorical connotation, connected more to literature or to the category of magic rather than to the strict taxonomic criteria. This is the opinion of the gemologist J. Nelson who ironically explained in 1985 that he turned to the London Zoo with the aim of determining the color of pigeons' blood by spectrophotometry: " The Burmese bird can at last be safely removed from the realms of gemmology and consigned back to ornithology".
Barbara Voltaire, Administrator of the reputable “GemologyOnline” website, coherently posted in 2007 that the term pigeon's blood is "archaic and non-quantifiable. It's analogous to defending the usage of River or Top Wesselton when describing diamond color. Certainly you could define them with comparable accepted terminology, but that's when the novelty would end".
This lasting reluctance of gemologists to take a metaphorical and evocative nomenclature might be explained by the particular care they show to be acknowledged as scientists belonging to the branch of mineralogy. For decades it seemed that the gemologist’s figure could be redeemed only by placing it under the protective wings of a constituted and well recognized experimental science. In absence of indisputable mineralogical procedures, the long journey started by Plinius and lasted up to the beginnings of the eighteenth century, was felt as the cause of the stagnation of the reasoning speech (logos) about gems in a puddle of methodological insecurity.
It is then in the middle of last century that gemology demands freedom of getting rid of that long lasting historical phase marked by the use of simple descriptive connotations. In fact, while resorting to metaphors, this habit had resulted in fruitless approaches to the cause of establishing measurement procedures in Mineralogy. A methodology based on arbitrary impressions, like referring to mining areas as quality assurance as well as evoking fantastic attributes, seemed to be deterministic and more appropriate to the sphere of magic.
Instead, it was necessary to entirely recover the authoritativeness of the mineralogical analysis, investigating the properties of crystals in a more and more sophisticated and comprehensive way.
In order to introduce the new parameters of quantitative measurement made available by the mineralogical techniques, gemology, to some extent, was re-built, at the expense of inevitably summary descriptions not relevant to well defined scales. Ultimately, outside an objective measurement environment, one might as well still remain conceptually blocked at Plinio's time.
On the contrary, the modern gemology willingly and definitively gained independence by breaking ties and abandoning the use of stories and tales, the long lasting approach initiated by the great Latin naturalist. Even R. Hughes, renowned for his deep knowledge of corundum as well as for his vision of a gemology open to emotional aspects and respectful of places and cultures, wrote in 2001: " Pigeon’s blood was the term used to describe the finest Mogok stones, but has little meaning today, as so few people have seen this bird’s blood"
Once standards are set why not talking again? GRS retrieves the hematic reference.
So no more pigeon blood but only vivid red? To some extent the attribute is confined to the dustbin, not being entitled to be taken into consideration in the main gemstone reports. But in 1996 GRS retrieves the term, using it in June 1998 for an octagonal ruby analyzed for Sotheby's. Dr. Adolf Peretti, CEO of GRS registers the Pigeon Blood trademark describing its criteria for classification (fig. 2). In Peretti's definition pigeon's blood grade is applicable to a certain group of natural rubies showing medium to high fluorescence, a vivid red color (high intensity and low tone, e.g. no brown and orange overtones). Chrome and iron (with presence of chrome always higher than iron in a ratio at least 2:1) have been identified as the agents producing that specific chromatic combination the pigeon blood originates from. Furthermore, according to Dr. Peretti, the definition is pertinent to all rubies no matter where they are mined from, if their features comply with the above mentioned parameters. Pigeon Blood can be a legitimate standing for heated rubies as well, at the condition that they received no diffusion treatment and no beryllium or fillers' addition.
Dr. Peretti himself reconstructs the investigation path which led him to reintroducing the term; he released a document (www.pigeonsblood.com) by which he points out that the scientific parameters in use are sufficient to guarantee an actual foundation of the terminology. Therefore the pigeon blood attribute does not refer as strictly as before to what Dr. Peretti depicts very well as romantizing literature, a sphere more properly belonging somehow to the strand of magic. Indeed GRS did nothing but technically restoring dignity, as a measurement standard, to those poetic elements previously banned by the more orthodox tendency of the scientific investigation. But apparently fairy tales remnants continue to float in the invisible underground stream flowing parallel to the chemical and physical analysis.
From now on, pigeon blood is again a fully legitimate and successful term in gemology as a result of a clear business need. Sotheby's, along with the big Auction companies, appreciate the reintroduced attribute because it is a part of the collective imagination capable to communicate the value and the preciousness to the general public. In short, market uses to send messages affecting the behavior of the gemological community. In the last fifteen years the hematic reference, after being reintroduced by GRS with a lot of master and protocol, is emerging timidly in reports of other major institutes. Indeed, but how?
As an example we take a recent case, occurred before the wider reintroduction of the pigeon blood grade. On May the 12th 2015, SSEF and Gübelin produced the gemological documents to accompany the sale of a gorgeous 15,046 carat ruby ring mined in the Mogok Valley mounted with two shield cut diamonds weighing respectively 2,47 and 2,70 carats (sold at CHF 28.250.000). A passage in the description contained in the report n. 78414 from SSEF is quite indicative. It says : "its vivid and saturated red color, poetically referred to as 'pigeon blood' is due to a combination of well-balanced trace elements in this stone, characteristic for the finest rubies from Mogok". When resorting to quotation marks and when underlining the term pigeon blood, the document betrays some kind of carefulness, almost an embarrassment as the attribute is mentioned. This is because it is necessary to balance its strong evocative power with a statement reaffirming that it is not to be regarded as a truly quantitative or qualitative connotation. These are not measurable data, and as such, are subjective or poetic, belonging essentially to the literary domain of magic. The red traffic light signal still bans from the gemological labs the pigeon blood readdressing it to the Zoo. The harsh statement of J. Nelson is still relevant.
Why hold back if the carousel is funny?
It is not about few cases. With the exception of GRS, all the most internationally reputable laboratories for decades have been scientifically reluctant to deal with a pigeon blood attribute devoid of objective connotations. Yet the gemstone market could not resist the romantic voice of the sirens singing the enchanting poem of pigeon blood, even if reported only in quotes and with discretion. Buyers of costly rubies ask the market to be gratified with something more than vivid red. Product and Price are at the top, now Promotion (the third P of marketing) is required to match the uniqueness of these wonderful rubies. And how can a gem be firstly promoted if not by the unchallengeable tool of a gemological statement? At this point the market trend demands that pigeon blood appears regularly as a measurement grade along with other qualitative and quantitative data, all useful to stress for promotional purposes the features of rarity and preciousness of rubies.
The watershed year is 2015. Finally the major players involved in gemological reports are convinced of the opportunity to characterize the pigeon blood color. Time has come for SSEF and Gübelin to release a joint communication on November the 4th in which they announce the setting of a master harmonizing their parameters to define pigeon blood as a color grade. The characteristics for identification are not different in many ways from the ones already established by GRS: “Pigeon blood red is best described as a red colour, with no apparent colour modifiers (such as blue or brown). A minute purplish tint is acceptable. The body colour 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".
In the absence of an internationally and agreed upon standard it would be recommendable to compare the color master used by GRS with the one used by SSEF and Gübelin. Additionally it remains to discuss to which extent the color of corundum is affected by more complex phenomena, other than the ratio of Cr and Fe or the action of fluorescence. According to Richard Hughes it seems that trapped hole color centers play an important role in the determination of the pigeon blood color as well as the path length determined by the size of the stone.
However, if we look at the parameters determining the pigeon blood color grade, substantial differences can be easily found. In fact, according to SSEF and Gübelin this grade is applicable only to un-heated rubies and only to those from a specific geographic location, the Mogok Valley or the Namiya district. No wonder that such a rule is not shared at all by Dr. Peretti who objects to denying the pigeon blood grade to gemstones having the same chemical characteristics, the identical combination of tone and saturation, for the sole reasons that they are mined outside that restricted Burmese area or that they received a heat treatment with no fillers.
The merits of a technical disputation are not among the purposes of these considerations. A wider harmonization process is likely to start and it is too early to speculate as to which parameters will prevail. It is, however, worth noting here the whole context of the analysis affecting the assignment process of a new color grade for rubies. It seems that the sense of indeterminacy we have noticed in the specialists while handling a terminology they perceive as poetic, has moved from the literary/magic level to a true technical/scientific level. In their press release of Nov. the 4th, 2015 SSEF and Gübelin underline the ambiguity prevailing among the experts while using a term not regulated by any conventional gemological standard. Therefore, while establishing new parameters founded on measurable properties, after all they both resort to unshared and arbitrary criteria. To make it short, being a poetic attribute, until not long ago the pigeon blood color was not considered fit to gemology classification; and now it is as unsuitable as before because the scientific standards adopted by the major players, being divergent turn to be somehow subjective again.
Once again gemology as a discipline must question the crucial relationship between the investigator (gemologist) and what is being investigated (gemstones). This relationship does not equate the one existing between the scientist (mineralogist) and the specimen. The latter is based only on a neutral intention of cataloging and archiving, whereas the object of investigation for a gemologist is to modify its economic value as a result of the categories he himself sets up. There are people in charge of defining the necessary and sufficient conditions to assign to gemstones a name evoking a magic sphere and not a mere alphabetical or numerical reference. These specialists are empowered by gemology to determine how much this name can or cannot qualify successfully the market status of certain stones.
The divergent parameters to identify the pigeon blood color grade in the area of vivid red can legitimately be seen as calculations of value that the gemological labs are proposing to the market. Consequently, for instance, a ruby from Mozambique having what it takes to achieve the pigeon blood color grade (Cr/Fe ratio and chromatic features) for GRS, will be ruled out by others. Interestingly, the setting of uneven parameters produces the consolidation of the economic value of pigeon blood rubies, although this may not be homogeneous. No matter in this regard how the status is technically obtained because the issue is less concerned with grading and much more related to a branding strategy. Different gemological parameters, the way they are stated in the reports, have little power to penetrate the awareness of the unskilled consumers. The general public will be reached only by the fascinating attribute known as pigeon blood in the sense of an effective trade qualification of excellence. Out of all these details nothing will pass to the stores but just a brand.
The brand of a jewel is supposed to consist of the set of values the producing company is historically able to express and convey. But can a brand exist for a gemstone? This is a status not automatically assignable, except to a minor extent, either by virtue of its geographical origin or by the consistency of the mining, manufacturing and distributing companies involved. These elements, having no strength to cross the supply chain, are not appealing or influencing consumers. To certify authoritatively and immediately the excellence of a brand the gemologist finds his way looking back at that parallel old path, providing him with the effectiveness of a smooth use of rediscovered poetic and literary descriptions.
Despite the attribute pigeon blood is missing even and shared parameters among the labs, its rescue clearly reveals how gemology approaches its development and which role assigns to itself. In the dichotomy, the objective character (quantitative classification) for a long time has prevailed over the descriptive character (poetic, literary, magic, subjective indications).
And this has come to equate the gemologist to the mineralogist, being both mere catalogers of species. Pigeon blood, anyway, expresses such a powerful appeal that it is worth a new parameter, different from vivid red. After retrieving a subjective connotation to make it objective, a quantitative color grade can be modified representing a mark of quality, that is a brand. This denotes a new phase that requires the gemologist to retrace his attitudes and the borders of his field of investigation. He might need again that background, inherited by the earlier descriptive phase that he looked bulky and awkward, being related to periods of ignorance or imperfect knowledge of the crystal chemical laws, the ages of superstition in the name of the magic. The old and rusty tools could be useful again at the condition that they are clothed in the respectability to be scientific and to depict efficaciously in the gemological reports the emotional factors, the stories, the poetry requested by the market, conditio sine qua non to strengthen the transmission of quality.
Suggested research material
Hughes R.,Pigeon's blood: Chasing the elusive Burmese bird, http://www.ruby-sapphire.com/r-s-bk-burma3.htm.
Van Gelder G.J., Precious stones precious words, in "Oh ye gentlemen. Arabic studies on Science and literary culture, pp. 313-332, Brill, Leiden, 2007.
A.A.V.V., Progetto Euromin, La storia della mineralogia attraverso i musei di mineralogia europei, http://catmin.geo.uniroma1.it/area_book/book/Storia%20della%20mineralogia%20(Euromin%20Progetto%20Raphael).pdf
Hughes R.,Pigeon's blood. A pilgrimage to Mogok, the valley of rubies.http://www.ruby-sapphire.com/pigeons-blood-mogok.htm
SSEF, Gübelin (press release), Switzerland’s SSEF and Gübelin Gem Lab agree to harmonise ‘pigeon blood red’ and ‘royal blue’ standardshttp://www.ssef.ch/fileadmin/Documents/PDF/Press_release_Pigeonblood_Royalblue_SSEF_GGL_final.pdf
Peretti A., An ethical debate concerning ‘pigeon’s blood’ rubies and ‘royal blue’ sapphires from diverse origins, http://gemresearch.ch/an-ethical-debate-concerning-pigeons-blood-and-royal-blue-for-corundum-from-diverse-origins/