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Batch of “Tourmalins”, native cut. On the left “gemmiferous gravel” bearing an extraordinary variety of colors
In the East, the word “tourmalins” does not mean “tourmaline“, but roughly translates into the word “semi-precious” or better, “semi-precious stones.” Occasionally we end up stumbling across lexical issues that lead to confusion and misunderstandings. Indeed, it is not at all clear where semiprecious stones end and where precious stone begin, but thus it is. We prefer the term “gems” that include both precious stones, and semi-precious stones, but language is a living entity, prolific in contradictions and bizarre rules by and large.
The fact is that many varicolored stones can be extracted from gemmiferous gravels in Sri Lanka. Once, it was easy to distinguish the corundum (rubies and sapphires), and all the other stones were named-out as “tourmalins“. Since certain areas chiefly produced garnet of excellent quality (to the point of giving them another name resulting in even more chaos: “Matara Ruby“), they have begun to differentiate garnets from other stones, although to date it is normal to find a certain amount of garnets in “tourmalin”-batches. Then it was the turn of alexandrite and cat’s eye quartz, which are tremendously valuable, and are therefore sought with great care.
And upto thirty years ago, it was normal to find ‘a bit of everything’ in “tourmalin”-batches: zircons, spinels, chrysoberyls, hessonites, rhodolites, spessartines, diopsides, aquamarines, sinhalites, kornerupines, tourmalines dravites, enstatites, andalusites, ganhites, etc. Today, even in Sri Lanka, where stonecutters are known for their approximation, the clearest samples of the weight of upto a few carats, are selected and processed with great care, because the collectible and rare stone markets have rightly stimulated and invigorated such research.
Today tourmalin batches are essentially composed of zircons, spinels, garnets and chrysoberyls, and these batches in particolar show a variety of very attractive colors. They distantly recall multicoloured tourmaline batches coming from Brazil; the main difference, perceivable at a glance, is that these stones, differ one from another both in their color and as well as in their blinding light.
Beautiful “Jagoon” of more than 30 ct .: the high birefringence of zircon is often visible to the naked eye, and this is the reason why some lines are seen bisected.
We are concerned with “Zircons“.
In Sri Lanka, when you are shown a large hazelnut brown color stone, of a darker tone though still bright, with a rather waxy surface shininess, they tell you that it is “Jagoon“. The thing that intrigued me, is that they pronounced such a name as if they were talking of a pleasant person, almost with affection, and I tried to understand which were the features that could possibily make it fun to be around such a serious-looking stone.
First of all, the stone must be big, because a small stone would not be fit to decorate the sacred elephant harnesses during the processions of “Poja Day”, the feast of the full moon. Then, you need it to weigh more than other stones. i.e. it must have a higher specific weight, and zircon is the best choice.
In zircon there are traces of uranium which, at some level, gives rise to displacements within the stone. This seed of life betroths well with the elephant, so long-lived, and with the Buddhist and Hindu religious traditions, which have been alive for thousands of years. This stone is thus committed to the elephant, to its power, wisdom, longevity, fondness, sacredness.
Photo 1 – When “tourmalins” possess a good weight and are of a good quality, they are processed with greater care and are offered for what they are: zircons, spinels, sinhalites, kornerupines, rhodolites, chrysoberyls, cinnamon stones, etcetera.
Photo 2 – Red zircon: stones of this color and with a weight of over 10 carats are quite rare.
Photo 3 – Batch of natural zircons of different colors.
Photo 4 – Green Zircon: the brilliant, shiny color of this stone will blur in a few million years, resulting in a metamittic zircon, with the color stretching towards brown.
In the early twentieth century, the smallest brown zircons were treated with a simple heat method, where it became white and blue. They were the substitute for diamonds of our grandparents: the high refractive index and good dispersion gave a good trick of the light. Even today, many think that zircon is a colorless stone look-alike for diamond, and this mixup mystification has increased with the placing on the market of a new synthetic product, the “cubic zirconia”, which has absolutely nothing to do with zircon at all.
The redder hue of zircon is called “hyacinth“, a name reminiscent of “Jagoon“, though referring to a different shade of color. G
reen zircon is the most disturbing. It announces the phase of slow destruction of the crystal lattice accomplished by the helium atoms emitted from that small amount of uranium, which will, in millions of years’ time, turn the stone into “metamittic zircon“, so that it becomes monofringent from the birifringent that it is, and military opaque green from the shrill green that it is.
Zircon crystallizes in many colors, from pale yellow to green, to almost black, to red; but its “real” color is “jagoon” which has a really nice hazelnut brown color, and it is a gem that I recommend especially to those who love elephants.
Specifications
Identification: Zircon.
Basic chemical formula: ZrO2SiO2.
Crystal system: Tetragonal.
Color: yellow, brown, green. With heat treatments you have the colors blue and uncoloured.
Hardness: varies from 6.5 to 7.5. Specific weight varies from 4.00 to 4.70.
Refractive index: varies from a minimum (1,79) for metamict minerals to an average value of 1,925-1,984. The high values are not readable on common refratometers.
Birefringence: very high, generally clearly visible with a simple magnifying glass.
Absorption spectrum: its examination under the optical spectrometer is the most difficult for students in gemology. Fortunately, there are stones such as zircon, that are rich in absorption and emission bands.
Origin: Sri Lanka, Indochina, Siam.
Notes: The gemological oddities of this stone depend to a large extent on the presence of traces of uranium inside it, causing a long-lasting turmoil at an atomic level, with the modification of physicochemical properties such as specific gravity, refractive index and color, during the corse of millions of years. This residual radioactivity is still minimum, and no cause for any kind of apprehension whatsoever. To date, synthetic zircons have not been manufactured in labs yet. However, other zirconium-based compounds have been constituted that are widely used in imitation jewelry, the “cubic zirconia”, with properties that are quite different from those of zircon. The similar name may cause confusion. Zircon is hard enough, but it’s still treated with respect, because it has the unpleasant inclination to get blunted at the corners. A certain cerous shininess is typical of this lovely, economic and little-known stone.
