Gem Testing:
from the separation of colors to the analysis the atomic Level
Ensaio sobre a história da gemologia publicado no número especial da newsleter do ICA Incolor, no número dedicado à directoria mundial de laboratórios gemológicos
in The ICA 2007 World Gemological Laboratory Directory, Winter 2007, pp.
por Rui Galopim de Carvalho
Long ago, when man began using and, most importantly, trading gem materials it became obvious that the perception of value was different for different materials, thus creating the need to name them, identify and separate them. At those early days through most of the Classical times, gem nomenclature and identification (if one may say so, though) was essentially performed by the simple observation of the most obvious external properties, like color, transparency, texture, etc. For example, due to the lack of a scientific base for separating the different gem varieties as we know them today, green gems like emerald, chrysocolla and some turquoise were grouped under the name smaragdus; red gems like ruby, spinel and garnet under carbuncle (or anthrax) and orange gems like hessonite garnet, tourmaline and sometimes zircon under jacinth. The works of Theophrastus (372-287 BC) and Pliny, the Elder (23-79 AD) are rich in such references. The same kind of empirical nomenclature is also patented in the Bible, most specially on the description of the 12 stones in the Breastplate of the High Priest, giving rise to very interesting interpretations even today.
Gem identification, for the sake of value perception and consequent justification of price, continued to be based in simple tests that were particularly well developed in the very advanced intellectual Islamic world of the 9th to 12th centuries, with the magnificent treatises on stones of Gabar ibn Haiyan, Al Beruni and later of Al Tifashi. In the western world though, the significant advances only started to take shape after the development by the Portuguese of maritime trading routes between the gem producing areas of the Orient and the consuming countries of Europe. Both academic scholars like Agricola and prominent goldsmiths like Benvenuto Cellini wrote on the identification of gem materials, being Cellini’s writings quite interesting in describing gem treatments and imitations.
Until the technological developments that offered commercially available synthetic stones in the dawn of the 20th century and most importantly the appearance of cultured pearls in the 1920’, most gemological problems were related to the identification of the materials, the detection of substitutes, like zircon and spinel, imitations, like pastes and “french pearls”, and other situations as doublets, foil backs, etc.
The 19th century was a prologue for the development of gemology as a knowledge field and, in fact, as a word in most languages. Not only did the industrial revolution plant the seeds of an emerging consuming middle class, but also the discoveries of more and new gemstone deposits boosted jewelry production. In this changing offer/demand scenario the geological sciences came into play, offering significant contributions to the development of the yet to be born gemology. The need for non-destructive methods for gem-identification was enough to mark the difference between mineralogy and gemology, creating the need for new instrumentation and procedures.
The first synthetic flame fusion (Verneuil) rubies in the world markets created some concern, namely in Great Britain where consequently gemology classes were being held around the country to assist the trade in dealing with the problem. The threat to consumer confidence that hit the markets after the spread of cultured pearls had a serious response by the industry with the creation in London of the first gem testing laboratory in 1925 headed by the famed gemologist Basil W. Anderson. More laboratories were founded worldwide after that, along with the spread of gemological education namely with the visionary work of Robert Shipley in what would become GIA since 1931.
The advances in the artificial growth of gem quality crystals to serve as substitutes of natural gemstones was accompanied almost side by side with the corresponded sophistication in the gem testing techniques to detect them, assisting the industry in maintaining trade and consumer confidence in jewelry products. The extensive research of the late Prof. Edward Gübelin in Switzerland on inclusions was one of these developments in gem identification under the microscope, but, very importantly, was the embryo of geographic origin determination of certain gemstones, like ruby, sapphire and emerald. In those days, in the mid 20th century, the issue of geographic origin covered only but a few important localities that had different levels of consumer value perception. For rubies there was basically Burma (Mogok) and Thai; for sapphire Kashmir, Burma, Sri Lanka and Australia; and for emerald Colombia, Brazil and a few African sources. Inclusions, refractive index, specific gravity, fluorescence, and other gemological properties were the basis for the production of an origin opinion. Then, the geological sciences gave once more solid contributions to gemology in this matter as some analytical methods became in common usage of gemological laboratories as confirmatory or necessary diagnostic tools not only for origin determination reports but also for more routine gem identification as new synthetics came into play.
If one takes some time analyzing the contents of the gemological literature in an historical perspective, we notice a that a few decades ago gem identification techniques, localities and synthetics made most of the titles. In the late 1980’s another subject became more and more persistent: gem treatments and enhancements. In fact, the 80’s and 90’s saw a huge evolution in the artificial processes that modify the appearance of gem materials, originating commercial availability of more gemstones that were creating new business opportunities for the whole industry, from mining to retail. These treatments soon created another question of value understanding and, in some cases, consumer confidence issues, somewhat like in the former days of cultured pearls, and therefore originated research projects that eventually culminated in the development of new techniques or in the adaptation of highly sophisticated mineralogical or geochemical analytical methodologies. This new diagnostic needs pushed gemologists even further and in some cases deeply into the fields of research chemistry, crystallography, crystal chemistry, mineralogy and so forth. More than ever, the answers to the relevant questions the market was presenting to better understand and communicate value lye on the material’s composition from the lightest element, like beryllium, and to the accuracy of a part per million (ppm) or even per billion (ppb). In some cases, it is crystal growth or other structural data hold the important information to those answers.
An increasing number of PhD thesis have been published year after year on gem related subjects every year and highly complex scientific contributions to gemology have also been presented to the gem and jewelry community at recent gemological meetings as both oral and poster presentations. The challenges of the new millennium for the gem and jewelry industry, not only due to treatments and synthetics, but also due to the a new consumer profile and consuming culture and new competitors in luxury goods and high-tech gadgets from outside the industry, have contributed to the strengthening of gemology as instrumental to the promotion of our industry’s transparency, to the sophistication and high-level of the gem trade laboratories and ultimately as a fundamental support to promote consumer confidence. As said right in the beginning, the consumer is the driving force of this gemological revolution, from color separation to the atomic level gemology and the information produced by the gem labs and printed on their reports, helps the industry in promoting value perception and trade transparency by promoting disclosure policies.
Artigos Internacionais
2007/05/30
Examinando lotes de rubis na Tailândia, procurando factores de qualidade.
© ICA Mining Report
