The Evaluation of Amber Gemstones
By Wieslaw Gierlowski
Comments may be address to Doug Lundberg at firstname.lastname@example.org
The Antiquity of Tradition
Baltic amber is perhaps the oldest stone used to decorate the human figure in the vast area of Europe. Not long ago, in the caves of the Pyrenees, home to the Aurignacian culture of 16,000 years ago, large (25 to 30 mm in diameter), round beads were found, formed of amber by human hands, belonging to those who considered this material to be so beautiful as to carry it over thousands of kilometres from a distant hunting journey to the north of Europe. Amber talismans in the form of pendants and necklaces from the late Palaeolithic, the Mesolithic and the Neolithic ages appear in numerous archaeological sites from the Ural Mountains to the British Isles.
However, it was only the ancient Mediterranean culture that introduced amber in the kind of goldsmithing works which we today would consider jewellery. This is certified not only by museum collections, such as the enormous accumulation of the most ancient decorations in the Archaeological Museum in Athens, but also in literary works full of admiration for the beauty of amber. Let me quote a passage from Homer's Odyssey:
"There came a man versed in craft to my father's house, with a golden chain strung here and there with amber beads. Now the maidens in the hall and my lady mother were handling the chain and admiring it, and offering him their price." [Translation by S. A. Butcher and A. Lang]
The most famous wives of the Roman emperors would wear grand sets of amber gemstones, including Livia, Messalina and Poppea, the wife of Nero, who loved amber in the reddish tint of her hair.
In time amber became an uncommonly popular and expensive gemstone in the Roman Empire. It was commonly used to decorate fibulae, pins for formal dress. The great demand for fibulae with amber led to such an enormous growth in their prices that Emperor Maxentius was forced to issue an edict on their official maximum. Such limits were imposed on only a few dozen luxury products on the Imperial market.
The Reasons for Success
Baltic amber, called succinite (from the Latin succinum) by geologists and mineralogists, has enjoyed enduring popularity over the millennia. This is due to its many virtues, but mainly to the conspicuous beauty of its innumerable varieties. That is is comparatively easy to work it with the use of many techniques is equally important. The abundance of amber's resources in deposits and accumulations as well as its occurrence both in the form of fine grains and quite large nuggets enable a wide variety of uses.
The largest nugget, excavated in 2005, weighs 5,960 grams. Photo 1 Such large specimens appear extremely rarely and usually end up in museum collections rather than in a jeweller's studio. Much more common are nuggets which weigh from a dozen grams to a kilogram, which given amber's low density, from 0.96 to 1.096 g/cm3, are quite large. This allows them to be used not only as gemstones, but also as a highly valued artistic material for sculptures and diverse decorative objects.
Large amber nuggets are well known to have provided the material for luxury jewellery boxes and furniture, and even for compositions on an architectural scale, such as the famous Amber Room or the Amber Altar, currently being built in Gdansk, which will exceed the Room's dimensions by almost one-half.
During the heyday of artistic amber jewellery making, which took place at the dawn of the modern era, and was influenced by the stylistic rules of the renaissance, baroque, rococo and classicism, amber was used mainly to produce works on a grand scale, without the use of precious metals. The artists focused on achieving artistic expression together with the precision of the structure. To assure the strength and durability of such large and complex works, made exclusively of pure amber components, which are inherently delicate and prone to mechanical damage is truly no easy task.
In contrast to contemporary times, metal settings were not used even in jewellery, for instance in beautiful necklaces made of sculpted elements or in relief medallions.
Today, amber is used mainly as a gemstone to decorate jewellery and small objects of applied art made of silver and gold, less frequently of other metals and alloys. The ability to bring out the maximum natural beauty of the nuggets has come to the fore. Equally important is the precision of the cut, the clarifying and the obtaining of the desired tints in stones for standard jewellery.
Several popular gemstones possess quite numerous colour varieties. None of them however, can compare with amber in this regard. It has thousands of colour varieties. It often happens that a single stone is a natural composition of over a dozen different colours.
Amber varieties also differ in the degree of their translucency. From completely clear specimens, which were once used to make eyeglasses and lenses for kindling fire (by the focusing of sunlight rays), through varieties translucent in various degrees, to completely opaque stones, often of the white or ivory variety.
Amber's great advantage is its lightness. This allows uncommonly large stones to be used in jewellery, which makes an impression of its dominance possible even when the weight of the stone does not exceed 20% of the total weight of the piece. Indeed, amber is 10 times lighter than silver and almost 20 times lighter than gold.
Amber can be excellently polished to obtain a gentle and noble sheen. A sheen which does not compete with the gemstones' natural range of tints, nor does it disrupt with its sparkle the form of the amber stones.
Amber gemstones are made with diverse methods of treatment. From the simplest methods, such as cutting, grinding and turning through to engravings and sculptures which produce gorgeous gems. Apart from amber cameos made of opaque varieties photo 5 in a full colour range, gems engraved and sculpted in intaglio at the bottom of transparent lenses, sheets, rose-cuts and many other gemstone forms are a true rarity. A picture engrave or sculpted in intaglio is adapted for viewing through the golden substance of the stone, while the curves or facets on its surface bring about an optical illusion of the movement of the depicted images and ornaments.
Amber gemstones satisfy not only the eye, but also the senses of touch and smell. Amber stones are always warm to the touch, and because of their negative static qualities they create a beneficial aura, which mitigates the impact of magnetic fields produced by most of the appliances around us. Necklaces and bracelets worn directly on the body, emit a delicate scent at body temperature, albeit below the sensitivity of the human sense of smell, but therefore unobtrusive while always there. Additionally, there is also the chemical impact of succinite's most valuable component: amber acid, a medicinal substance, which other fossil resins do not have.
In summary, we can say that amber's comeback as a universally known and valued gemstone is perfectly justified by its tradition and valuable properties. On condition, however, that one can verify its authenticity and the positive and negative features of its treatment.
The classification of amber gemstones according to their production method The International Amber Association in Gdansk, which associates the manufacturers and merchants of Baltic amber products from all the countries in which there is significant manufacturing or trade in these products, has established the following basic classification of amber gemstones depending on the method of stone production, the degree of intervention in the nature of their substance and their objective value:
Natural Baltic amber (succinite) - subject only to mechanical processing (for example grinding. cutting, turning, polishing) without any changes to its natural properties.
Improved Baltic amber (succinite) - in which changes in the physical properties, including transparency and colour, have been artificially induced through thermal treatment. photo 11 Combined Baltic amber (succinite) - consists of two or more parts of natural, improved or pressed Baltic amber glued together with an appropriate colourless binding agent.
Pressed - reconstructed Baltic amber (succinite), a gemstone made of amber crumbs, amber meal or amber crumbs and meal pressed at high temperatures and high pressure without additional ingredients.
In order to highlight or change the natural colour of the amber, the use of precious metal foil or flakes and colour backdrops made of enamel and paints in jewellery products decorated with Baltic amber (succinite) gemstones is allowed; the painting of the bottom of the stones, however, is not allowed.
The classification presented above does not allow the classifying as amber gemstones: products made with the addition of artificial or synthetic plastics, much less products made by sealing amber grains in a large amount of polyester resins. These are better or worse amber imitations and marketing them as real amber products is considered an act of forgery.
The classification determines the value of each gemstone category, ranking them from the most valuable to less valuable.
Stones made of natural Baltic amber (succinite)
This category does not include stones made of other fossil resins, even from resins which appear together with succinite in common deposits, such as: gedanite, glessite, beckerite and stantienite. Gemstones made of fossil resins from various parts of the globe which are used there for the manufacturing of jewellery items, widely called amber, do not belong to this classification category either. This concerns even such rare and valuable minerals as Sicilian amber and the more popular Dominican, Mexican and Saravac amber. Nor are Burmite and rumenite, which have certain traditions as artistic materials, on a par with succinite, but constitute another initial material for gemstones.
The most valuable among gemstones made of natural Baltic amber, i.e. succinite, are those in which the grinders manage to bring out their unique colour beauty and at the same time retain a semblance of the natural form of the nuggets. Such a premise automatically imposes efforts to produce a unique setting which would integrate the unique stone with the precious metal into a single unique gem. photos 14,15,16 Gemstones made of naturally transparent nuggets full of warm golden colour, at the bottom of which a layer of bark has been retained to give a beautiful reflection and the impression of a close bond with the amber's organic nature, are both beautiful and valuable. photo 17 Amber transparent by nature, rarely found in primary deposit mines, but quite often found in secondary deposits (today, mainly under the sediments in the Vistula River Delta), is perfect for making gems in intaglio.
Images sculpted in such material are delicate, just a shade brighter than the rest of the stone. They are easy to tell from gems made of thermally improved amber stones whose inside is discoloured to a watery shade while their surface is usually roasted to a dark cognac or red colour. There are of course those who like such contracting compositions, however in the opinion of the experts of the International Amber Association, they are clearly inferior to gems made of natural amber. photos 18 and 19
There is still a large demand in the market for perfectly made, but rather monotonous semispherical and elliptic cabochons and beads in the form of spheres and regular olives. They are thoroughly secured in distant tradition when obtaining such regular forms in primitive workshops was a kind of masterpiece. photo 20
Regularly formed, pure, natural tear shaped nuggets are also highly valued. photo 21 Such forms are very expensive because their turning causes enormous losses (ca. 80%), the reason being that amber rarely appears in rounded forms in nature.
Beads which are faceted after turning, akin to crystal cuts, are even more expensive. The regular covering of the beads' surface with glittering facets while retaining clear edges goes against amber's very nature, which is rather prone to rounded forms and a soft glow. This makes the process very difficult.
Amber's natural forms are sometimes used as gemstones, for example in the form of drops, icicles or congealed cascade dripstones. In dripstones, one can most often find sealed traces of ancient life, called inclusions. The price of specimens with inclusions differs depending on the clarity and the scarcity of the sealed animals and plant fragments.
Stones made of improved Baltic amber (succinite)
For a very long time, the manufacturers of ready products and gemstones made of amber have been trying to influence their appearance through physical and chemical intervention, usually combining both methods. As early as in ancient Rome amber was clarified and tinted by cooking in oils with the addition of dyes. The surface of the gemstones was also saturated with saffron (Anchusa tinctoria) extract, which has the property of not paling with time, but it gradually turns from golden to orange-red, just like amber.
Procedures meant to improve the appearance of amber or to adapt it to the current fashion trends, however, were not very common until the mid-19th century. Before that time, amber jewellers used material obtained from the sea or from post-glacial accumulations, which had been subject to natural transformations during its travel from the primary deposits to the place where it was gathered, fished or dug up from shallow layers of earth. Before the deep mines in the Sambian Peninsula were built, jewellers would deal with largely transparent or translucent material, useful for forming gemstones without any intervention in its structure.
Mines built on primary deposits, which are the dominant source of supply today with an over 90% share of the total mass of material, usually provide material which is different from the traditional variety: opaque and poorly coloured (waxy, yellow with greenish shades, white and ivory amber). Meanwhile, current fashion demands clear stones with an intense colour: honey, cognac or various shades of red to crimson and cherry.
This situation called for the construction of devices which would accelerate the natural processes of amber clarification and its obtaining of the desired colour. Such a device is the commonly used autoclave, a chamber stove filled with noble gas (argon or nitrogen) under considerable pressure. The pressure of the gas in the stove chamber during the heating rises from several dozen atmospheres to as much as 300 kg/cm2. Amber heated to a temperature above 200oC softens, while the gas bubbles it contains (which are the cause of the initial opacity) close up and the material becomes perfectly clear. Unfortunately, it also loses its true amber colour of saturated gold. It becomes almost colourless, only watery-greenish. In order to obtain the impression of intense colour it is necessary to perform an additional operation of roasting ready stones in normal atmosphere, so that they a thin colour layer on their surface obtain (as a result of oxidising). A third operation is also sometimes used to improve amber, or rather to adapt it to the customers' taste. It produces characteristic cracks, known as scales or, by the German term, "blitzes" i.e. flickers.
During the thermal operations described above, the amber becomes somewhat harder, less fissile and uniform in terms of transparency and colour. This makes it easier to establish standards when handling large batches of products in the wholesale trade. It makes it possible for the contracting parties to agree beforehand as to the exact shade of colour or "scale" effect or whether to refrain from this operation. However, this also means giving up a very important feature of amber's nature: its multiple colours.
The roasting of amber in autoclaves, in an atmosphere of noble gases leads to one more characteristic symptom. It colours the natural weathered layer on the nuggets' surface black, and the thin layer of bark greenish. The retaining of such a layer on the bottom part of cabochons makes them somewhat resemble the green variety of amber, seldom found in nature.
An experienced commodity expert will notice the differences between such stones with the naked eye, but dishonest manufacturers and merchants often try to deceive their customers. The next step compounding such a forgery is to paint the bottom of the stones with binding agent-based paints which aggressively penetrate the porous weathered surface. Blue, green or even black dyes are used, often in a thick covering layer. photos 23,24, 25 It is easy to imagine how risky such a forgery is given the possibility of the quick chemical disintegration of the binding agents and the cracking of the entire bottom of the stone. Such acts have been deemed unworthy by all the Polish professional and economic associations in the amber jewellery industry. We hope that in the future the organisers of jewellery trade exhibitions will introduce the requirement to clearly label stones with painted bottoms, which is the case with pressed amber.
Here, I would like to refer to the controversy concerning the painting of amber gemstones, which arose at an international scientific conference related to the opening of the reconstructed Amber Room in Tsarskoye Selo. The Russian masters who conducted the reconstruction work faced the problem of the exact recreation of the colour composition on large stretches of walls using a material which is different from the sea amber used in the original decor. For over a dozen years, the Leningrad Technological Institute worked to find the paints which would provide the appropriate colour range, be durable and which would not damage the amber. These paints were finally developed and patented (with two postdoctoral theses being written in the process), and then used to cover the entire surface of the walls' decor. However, the opinion of foreign specialists, including Prof. Alexander Shedrynsky, a renowned researcher and practitioner in amber conservation from New York, was full of reservations and warnings against the harmful effects of painting, even with especially selected substances.
Stones made of combined Baltic amber (succinite)
Amber stones made of two or more combined elements are rare at the AMBERIF Fair. Sometimes, however, the combining of a number of varieties of amber into a well-thought-over colour arrangement yields a beautiful and one-of-a-kind effect. Apart from a desired artistic expression, this method requires the use of the appropriate colourless binding agents in minimal layers, which do not compete with the amber. Multicoloured arrangements with the significant use of synthetic resins are classified as amber imitations according to the classification regulations of the International Amber Association.
Stones made of pressed - reconstructed Baltic amber (succinite) Succinite, just like a number of other fossil resins, has the ability to join permanently its small fragments heated in the appropriate moulds to a temperature of over 140oC (usually between 200 and 220oC) pressed at high pressure. A uniform mass is obtained already at a pressure above 200 kg/cm2, but the best results are obtained at a much higher pressure: about 1,250 kg/cm2.
In order to obtain a uniform colour of the pressed amber pieces and the desired degree of transparency of the material, it is necessary to remove the external weathered surface completely and to perform a selection of the material by rejecting grains with organic and mineral impurities. The act of pressing takes place in an atmosphere of noble gases, after the air has been sucked away. Failure to perform this procedure yields a material with conspicuous red streaks, and even with an ugly dirty-greenish tint.
Like natural amber, pressed material can be corrected through thermal processing in autoclaves. Oftentimes, "scales" are deliberately made in these stones in order to conceal quality defects.
Some manufacturers use this as a way to hide from merchants that their gemstones were produced from pressed amber, rather than amber nuggets. It is very difficult to differentiate well fabricated pressed amber products from thermally improved amber and it is possible only at large magnifications under a microscope or through examining the differences in their fractures, which however damages the examined product.
Pressed amber stones which contain pigments are easier to tell from natural amber. Colour varieties dissimilar to those made by nature are often made in this way.