(via The Journal of Gemmology, Vol.13, No.8, October 1973) J M Ogden writes:
Since the brief note on Roman imitation diamonds by the writer was published in the Journal of Gemmology two fine Roman rings, both set with interesting stones have been available for study. The first has an attractive openwork-sided setting in which is set an octahedral stone. This stone was at first glance taken to a rock crystal of the type considered by the writer to be a Roman imitation of a natural diamond crystal. Closer inspection of the stone however revealed the typical surface decomposition characteristics of glass and the stone was, in fact, a yellowish white glass (the term paste would be wrong here, as technically this should only refer to those glasses with high refractive index and brilliance). The writer knows of other instances of rings set with glass octahedral, and these, like the rock crystals, might be taken to be imitations of diamond crystals. It might be argued that any reasonably knowledgeable Roman could have told glass from the invincible diamond, but one would expect that these copies of diamond crystals were more in the nature of moral frauds; in other words they would have been worn by those to whom the diamond was, for reasons of economy or rank out of reach. A similar state of affairs can be seen earlier in the Roman period when only free-born citizens were allowed to wear gold rings; slaves and others made do with wearing gilt bronze rings.
The second ring is extremely interesting and possibly even unique, as it is set with a brown diamond. This stone, larger than any other Roman diamond known to the writer, is in the form of rough natural twin octahedral. Alec Farn of the Gem Testing Laboratory very kindly examined and tested this stone and found it to be a brown-series diamond: two lines, at 4980 Angstrom, were visible in the spectrum, and there was a blue fluorescence under X-rays. The weight of the stone was difficult to gauge, but it must have been about 7 carats. The majority of the Roman diamonds known to the writer do not have recorded weights, but they generally would seem to weigh under a carat. This large stone under discussion was by no means obviously a diamond from color or appearance, except to one versed in crystallography; so other stones of a similar nature might exist, unrecognized, in museum or private collections. In its recent history the stone in this ring has been described in a multitude of ways, most recently as ‘Topaz’. This fine ring is of a similar type to the first ring mentioned above, although it is sturdier and its size would indicate that it was definitely a man’s ring. Both these rings were originally in the collection of Count Henri de Clercq Boisgelin, a well-known collector whose ancient jewelry included some of the finest specimens known. There is no cause to doubt that both these rings are genuine, and that they date from the late Roman period (c. 3rd - 4th century A.D). Close examination by the writer revealed no evidence that the stones were not originals: indeed the ring holding the diamond had quite obviously been made for that stone and none other. The coloration, surface appearance under strong magnification and the general ‘feel’ of the gold in both cases would show that the settings were as old as supposed.
No provenance is recorded for either of these rings, though it would seem likely that they were made in Italy or in one of the Eastern Roman centers such as Asia Minor or Egypt. The exact area of origin for the diamond is not known, but it would be likely that it was traded ‘loose’ from India, possibly via Alexandria.
Sunday, July 08, 2007
Gemmology On A Shoestring
(via The Journal of Gemmology, Vol.10, No.3, July 1966) B W Anderson writes:
Hardness
Hardness as a test has always been considered taboo amongst gemologist, partly because of the danger it implies of damaging the specimen tested, and partly because of its inexactness compared with refractive index or density determinations. But hardness has a marked influence on the degree of polish that a stone can take and maintain and thus affects the appearance of a stone. The sharp facet edges in diamond, for instance, help one to distinguish it from strontium titanate, where the edges often have an almost molded appearance. It is as well to realize that hard stones such as sapphire or even diamond may show an astonishing degree of wear, and one should be careful to avoid jumping to conclusions on this evidence alone. Since the hardness of diamond is unique, a careful trial with an edge of a suspected diamond on a piece of synthetic corundum is sometimes justified. If the specimen ‘bites’ on the corundum and leaves a definite mark, there is nothing else but diamond that it can be. Before the test is done, the corundum surface should be examined with a lens to ensure that no scratches are already there on the part that is to be used; and any mark made by the diamond should be rubbed with the finger and examined with a lens to ensure that it really is a scratch. With jade and the jade-like minerals gentle trials with a knife blade or needle point may yield valuable information, but should only be used where other tests fail, and when one can be sure that no damage results to the specimen. One should also recognize that there may be considerable variations in the hardness of such materials.
Density
Before the coming of the jeweler’s refractometer devised by the late Dr Herbert Smith, tests for specific gravity (density) were the only accurate means of determining the nature of any unmounted gemstone. It remains a thoroughly useful test for any stone free from its setting. Every gemologist knows that a simple trial in a heavy liquid will distinguish at once between yellow quartz and true topaz, or between quartz or chrysoberyl cat’s eyes. To make these distinctions by the ‘feel’ or ‘heft’ of the stone in your hand is a decidedly tricky business, but worth practicing. Even when strung a necklace, the extreme ‘lightness’ of amber can be noticeable, when compared with bakelite or other synthetic resins. The judgment of the weight of a stone in relation to its ‘spread’ is, of course closely bound up with a knowledge of its specific gravity, and here again the gemologist scores.
Cleavage
Where a stone has a marked cleavage, traces of this can often be noticed as flaws or incipient flaws within the stone or on the surface, where any nicks or chips may be seen to have flat sides instead of curved surfaces as in a conchoidal fracture. Cleavage nicks can often be detected round the girdle of a brilliant cut diamond, especially if the stone had been removed from a setting. This adds one more to the many revealing signs that one can find when examining a diamond.
Surface structures
This is rather a comprehensive heading, and can be used to cover such things as the traces of untouched crystal surface (naturals) that can often be detected on the girdle of a cut diamond; similar structures on the rear facets (really crystal faces) of a Lechleitner synthetic emerald, where the overgrowth is purposely left to enhance the color; the ‘flame’ pattern which is so completely distinctive for pink (conch) pearl, and so different from the grained structure of coral; the ‘engine-turned’ pattern on the surface of ivory; the dimpled surface of the fine jadeite; the demarcation line (nearly always above the girdle) marked by a sharp change in luster, when the surface of a garnet-topped doublet is examined in reflected light; the short, parallel crack-like markings (fire marks) due to careless cutting, seen only in corundum, more particularly in synthetic ruby or sapphire; and so on. A complete list of surface signs would be a very long one.
Internal structures
Internal structures or ‘inclusions’ should not really have come so late in the batting order, since such features are often of enormous help in identifying different gemstones and in distinguishing natural stones from their synthetic counterparts. But to study inclusions in their full beauty and detail one undoubtedly needs to examine them under a microscope—preferably a binocular microscope, and immersed in a cell of suitable fluid. Even with a pocket lens some inclusions are completely distinctive: for instance, the ‘horsetail’ inclusions of asbestos fibres which are almost invariably to be seen in demantoid garnet, and the ‘silk’ which is so typical a feature of Burma ruby. In both these cases of course the color and appearance of the stone will already have put you on the right track. The list of such ‘deadsure’ identifications by inclusions I not a very long one, however, except at the gifted hands and eyes of a master of the subject such as Dr Edward Gubelin. One should, however, be certain of an amethyst which shows the curious ‘tiger-stripe’ inclusions; of ‘goldstone’ (aventurine glass) with its glittering triangles of included copper; of a paste when it shows a typical elliptical bubble or so and of a doublet when a layer of bubbles can be seen at the surface where garnet meets the glass. Hessonite garnet, of course, is usually easy to detect with its crowded inclusion-picture of diopside crystals in a treacly golden brown setting. The curved lines in synthetic ruby may be too finely spaced for a lens to detect, but in sapphire the broader curved swathes of color are often more visible to the lens than under the microscope. The stone should be viewed against the white background of a sheet of clean paper or blotting paper, and turned in different directions until the right angle for viewing is found. Immersion in liquid will often help here (I am jumping ahead a little) and will also reveal the straight-sided bands of color so typical of natural sapphire. The ‘feel’ of a stone and its ‘coldness to the touch’ may also on occasion provide evidence of its nature.
Gemmology On A Shoestring (continued)
Hardness
Hardness as a test has always been considered taboo amongst gemologist, partly because of the danger it implies of damaging the specimen tested, and partly because of its inexactness compared with refractive index or density determinations. But hardness has a marked influence on the degree of polish that a stone can take and maintain and thus affects the appearance of a stone. The sharp facet edges in diamond, for instance, help one to distinguish it from strontium titanate, where the edges often have an almost molded appearance. It is as well to realize that hard stones such as sapphire or even diamond may show an astonishing degree of wear, and one should be careful to avoid jumping to conclusions on this evidence alone. Since the hardness of diamond is unique, a careful trial with an edge of a suspected diamond on a piece of synthetic corundum is sometimes justified. If the specimen ‘bites’ on the corundum and leaves a definite mark, there is nothing else but diamond that it can be. Before the test is done, the corundum surface should be examined with a lens to ensure that no scratches are already there on the part that is to be used; and any mark made by the diamond should be rubbed with the finger and examined with a lens to ensure that it really is a scratch. With jade and the jade-like minerals gentle trials with a knife blade or needle point may yield valuable information, but should only be used where other tests fail, and when one can be sure that no damage results to the specimen. One should also recognize that there may be considerable variations in the hardness of such materials.
Density
Before the coming of the jeweler’s refractometer devised by the late Dr Herbert Smith, tests for specific gravity (density) were the only accurate means of determining the nature of any unmounted gemstone. It remains a thoroughly useful test for any stone free from its setting. Every gemologist knows that a simple trial in a heavy liquid will distinguish at once between yellow quartz and true topaz, or between quartz or chrysoberyl cat’s eyes. To make these distinctions by the ‘feel’ or ‘heft’ of the stone in your hand is a decidedly tricky business, but worth practicing. Even when strung a necklace, the extreme ‘lightness’ of amber can be noticeable, when compared with bakelite or other synthetic resins. The judgment of the weight of a stone in relation to its ‘spread’ is, of course closely bound up with a knowledge of its specific gravity, and here again the gemologist scores.
Cleavage
Where a stone has a marked cleavage, traces of this can often be noticed as flaws or incipient flaws within the stone or on the surface, where any nicks or chips may be seen to have flat sides instead of curved surfaces as in a conchoidal fracture. Cleavage nicks can often be detected round the girdle of a brilliant cut diamond, especially if the stone had been removed from a setting. This adds one more to the many revealing signs that one can find when examining a diamond.
Surface structures
This is rather a comprehensive heading, and can be used to cover such things as the traces of untouched crystal surface (naturals) that can often be detected on the girdle of a cut diamond; similar structures on the rear facets (really crystal faces) of a Lechleitner synthetic emerald, where the overgrowth is purposely left to enhance the color; the ‘flame’ pattern which is so completely distinctive for pink (conch) pearl, and so different from the grained structure of coral; the ‘engine-turned’ pattern on the surface of ivory; the dimpled surface of the fine jadeite; the demarcation line (nearly always above the girdle) marked by a sharp change in luster, when the surface of a garnet-topped doublet is examined in reflected light; the short, parallel crack-like markings (fire marks) due to careless cutting, seen only in corundum, more particularly in synthetic ruby or sapphire; and so on. A complete list of surface signs would be a very long one.
Internal structures
Internal structures or ‘inclusions’ should not really have come so late in the batting order, since such features are often of enormous help in identifying different gemstones and in distinguishing natural stones from their synthetic counterparts. But to study inclusions in their full beauty and detail one undoubtedly needs to examine them under a microscope—preferably a binocular microscope, and immersed in a cell of suitable fluid. Even with a pocket lens some inclusions are completely distinctive: for instance, the ‘horsetail’ inclusions of asbestos fibres which are almost invariably to be seen in demantoid garnet, and the ‘silk’ which is so typical a feature of Burma ruby. In both these cases of course the color and appearance of the stone will already have put you on the right track. The list of such ‘deadsure’ identifications by inclusions I not a very long one, however, except at the gifted hands and eyes of a master of the subject such as Dr Edward Gubelin. One should, however, be certain of an amethyst which shows the curious ‘tiger-stripe’ inclusions; of ‘goldstone’ (aventurine glass) with its glittering triangles of included copper; of a paste when it shows a typical elliptical bubble or so and of a doublet when a layer of bubbles can be seen at the surface where garnet meets the glass. Hessonite garnet, of course, is usually easy to detect with its crowded inclusion-picture of diopside crystals in a treacly golden brown setting. The curved lines in synthetic ruby may be too finely spaced for a lens to detect, but in sapphire the broader curved swathes of color are often more visible to the lens than under the microscope. The stone should be viewed against the white background of a sheet of clean paper or blotting paper, and turned in different directions until the right angle for viewing is found. Immersion in liquid will often help here (I am jumping ahead a little) and will also reveal the straight-sided bands of color so typical of natural sapphire. The ‘feel’ of a stone and its ‘coldness to the touch’ may also on occasion provide evidence of its nature.
Gemmology On A Shoestring (continued)
Barytes
Chemistry: Barium sulphate
Crystal system: Orthorhombic; crystals often tabular; massive & stalagmatic form; rosette aggregate form.
Color: Transparent to opaque; colorless, blue, yellow, red, brown, green; massive white.
Hardness: 3
Cleavage: Perfect; in 3 directions, brittle; Fracture: uneven
Specific gravity: 4.3 – 4.6
Refractive index: 1.636 – 1.648; Biaxial positive; 0.012
Luster: Vitreous
Occurrence: Worldwide; Canada, USA, England, Germany, Spain.
Notes
Barytes is also called Barite (or Heavy Spar); massive white may resemble marble; some shows stalagmatic formation; crystal aggregates in the form of rosettes is often known as ‘desert roses’; fluorescent specimens may show faint blue/green colors; usually cut for collectors.
Crystal system: Orthorhombic; crystals often tabular; massive & stalagmatic form; rosette aggregate form.
Color: Transparent to opaque; colorless, blue, yellow, red, brown, green; massive white.
Hardness: 3
Cleavage: Perfect; in 3 directions, brittle; Fracture: uneven
Specific gravity: 4.3 – 4.6
Refractive index: 1.636 – 1.648; Biaxial positive; 0.012
Luster: Vitreous
Occurrence: Worldwide; Canada, USA, England, Germany, Spain.
Notes
Barytes is also called Barite (or Heavy Spar); massive white may resemble marble; some shows stalagmatic formation; crystal aggregates in the form of rosettes is often known as ‘desert roses’; fluorescent specimens may show faint blue/green colors; usually cut for collectors.
Saturday, July 07, 2007
Swarm Theory
The concept does makes sense in the gem and jewelry business. There is a link, and the behavioral pattern of the dealers, jewelers and consumers in the gem and jewelry sector are no different from ants, bees + other group (s) mentioned in the article. Though strange, you will have to 'see through' to understand the importance of swarm behavior.
Peter Miller writes about swarm intelligence + insights that can help humans manage complex systems + the complex behavior of a group + other viewpoints @ http://www7.nationalgeographic.com/ngm/0707/feature5/
Peter Miller writes about swarm intelligence + insights that can help humans manage complex systems + the complex behavior of a group + other viewpoints @ http://www7.nationalgeographic.com/ngm/0707/feature5/
Restructured DTC to Focus Solely on Rough Distribution as Core Business
Chaim Even-Zohar writes about modifications in the Diamond Trading Company’s (DTC) Sightholder selection process + the impact on sightholders + other viewpoints @ http://www.idexonline.com/portal_FullEditorial.asp
For Gemology Students
Dr Edward Gubelin is an inspiring icon (forever). He explains in his usual colorful tone how to connect gemology with other faculties of science (s) + to act with a sense of responsibility + gemology without conscience is the undoing of one's soul + to be honest and always tell the truth.
Dr Edward Gubelin's Address
In his address, following the presentation of awards to the Gemmological Association of Great Britain at Goldsmith’s Hall on 25th November, 1974, including candidates from many different parts of the world, Dr Edward Gubelin said:
What is happening on our planet today? I do not mean the belligerent tensions in the near East nor the failure to adopt a common energy policy nor the worldwide monetary crisis—no, what happens in this world as an entity, what happens at the present for the first time uniquely and so thoroughly that it will be remembered in the centuries to come, just a we still acknowledge and appreciate today the invention of the wheel, of the alphabet, the development of the great religions of the world, or from a geological point of view the folding up of the Alps, as an outstanding and irrevocable phenomenon. Well, what is happening in front of our eyes today? It is a tremendous and in its kind certainly a unique metamorphosis, which could at best compare with the change which mankind underwent during the dark ages and then again at the beginning of the Renaissance. The world happens to be in the midst of a fundamental change of structure with biological, physiological, sociological and even theological effects, and these are of such profundity that we cannot escape them.
To a certain extent we have been experiencing drastic changes also in our profession. Until recently, our idea of sales promotion moved along perspectives which had already been fixed in medieval times and which were almost exclusively limited to the mere action of selling, and best to a successful sales talk, while today after a short time of transition (calculating just a few years) great value is being placed in an extensive professional erudition, profound psychology, sound argumentation and efficient advice. While previously the old Roman warning Caveat Emptor, which originated from distrust, alerted the buyer to be careful, it now has the meaning that the client wishes to be well informed and accurately advised about the goods he is interested in purchasing. This desire may only be fulfilled by the salesman if he masters a fundamental professional knowledge. Science reigns today over all sequences of our life, medicine a well as commerce, production as well as communication, and the last consumer wishes to share in this professional science.
It is the aim of the gemological courses, which you have so successfully completed, to offer this specialized knowledge which will give you greater self-assurance and consequently increase well founded trust to assist your clients in such a way as to justify the confidence they place in your hands. The relatively broad spectrum of knowledge taught in the condensed form of, say, 25 or 30 assignments distributed over two courses challenged your capability to understand connexions and relationships which exist between different disciplines of the science of nature as well as between different properties of gemstones. The capacity of thinking in relationships and coordinations as well as the readiness to engage yourselves and to take responsibility and to accept solidarity should, apart from your technical achievement, be the human or spiritual benefit of your gemological study. In this sense, I wish to congratulate your most cordially on your successful attainment, which is the well deserved result of your perseverance and brave sacrifice during two years of intensive study. Not only your personal interest in gemology has led you to this award but also your thirst for knowledge and education, that marvelous, growing, aching process, whereby the mind develops into a usable instrument with a collection of proved experiences from which to function.
Some of you may consider the diploma examination as the climax of your gemological studies. Yet, may I bring to mind that this is rather the first ‘rung of the ladder’—that you have merely just crossed the threshold of a space spreading before you with no visible horizon, and the heady sensation you may feel now is only the beginning of further studies combined with unexpected experiences which perhaps are more closely linked with your practical everyday life in future. Therefore I recommend you to remain abreast of future developments by joining the advanced post diploma courses and subscribing to gemological periodicals.
Your diploma should not mislead you to consider yourselves as infallible experts. Your status quo is comparable to the situation of a young B.Sc or Ph.D who has just received his academic title, which does not attest him yet as a fully fledged scientist but merely that he has learnt to think and act independently and—as is to be hoped—with a sense of responsibility.
Among the resources offered to the modern science of nature gemology assumes a prominent place. Unfortunately it was considered a superfluous appendage and hardly acknowledged for almost a generation, and gemological publications only appeared as foot notes to mineralogical literature. Yet, indeed, as an independent basis, gemology has often supplied mineralogy with fundamental data and proved to be of invaluable assistance. Gemology was lacking professionalism for a long time and for far too long gemology was merely a trade accessory. Gemological degrees at present are still no more than school degrees, either rewarded by trade associations or by private institutes affiliated with the trade. An academic degree course would help in upgrading the profession’s standing similarly as university training would facilitate gemology and gemologists to meet the increasing technology and standard of investigation.
However, thanks to numerous outstanding achievements in highly scientific gemological research, today gemology is fully recognized as a science. As a matter of fact, gemology is today rightly entitled to claim the merit of having essentially contributed towards the astonishing progress of mineralogical research. The endeavor to expand as far as possible the boundaries within which may be possible, is a central motive of technical and scientific development. It is the same force which led our progenitors to master the use of fire and which drives us today to investigate outer space without knowing where this may lead us to. This intense desire of mankind to question all boundaries again and again is already grappled in the Genesis of the Old Testament by the words ‘Conquer the Earth with all that is within’ and thus deprived of any further argumentation. However, if man conquers the Earth, then he must corroborate by his mental disposition as well as by his moral conduct that he is indeed legitimized for this role—not only a scientist but also in his quality as a human being.
By this I mean to emphasize that we have a right to profit from our knowledge to our own personal advantage, yet never to use it to the harm of others. A French philosopher expressed this thought with the following word: ‘Science sans conscience n’est que ruine de l’ame’—science without conscience is the undoing of one’s soul. Scientific research means searching for the truth. Consequently, we are obliged to be honest and always tell the truth, and if we happen to make a mistake we should summon the courage to admit it.
Irrevocable laws do not only exist in the field of the sciences of nature but also in the sphere of human life and coexistence. In this connexion I may refer to the problematics of liberty and restraint, to all the tensions which occur because man is a personality who must develop in freedom, yet according to the laws of nature he is also a social being, who can only completely unfold himself in a society. It may not be superfluous to remind ourselves of this fact today, when sometimes righteously, but more often with no right whatsoever, scientific or social achievements are assaulted and when the behavior of certain unscrupulous people assumes a most aggressive character. The essence of the intrinsic virtue of the thing stipulates a much more positive and courageous mind, in social, public, religious and scientific domains, in order to defend all these accomplishments of mankind and save them for future generations.
In this sense I bid you a successful future resulting from your freshly acquired gemological knowledge; may many interesting tests be the source of personal satisfaction and happiness to you and the reason of increasing confidence placed in you by your clientele.
Dr Edward Gubelin's Address
In his address, following the presentation of awards to the Gemmological Association of Great Britain at Goldsmith’s Hall on 25th November, 1974, including candidates from many different parts of the world, Dr Edward Gubelin said:
What is happening on our planet today? I do not mean the belligerent tensions in the near East nor the failure to adopt a common energy policy nor the worldwide monetary crisis—no, what happens in this world as an entity, what happens at the present for the first time uniquely and so thoroughly that it will be remembered in the centuries to come, just a we still acknowledge and appreciate today the invention of the wheel, of the alphabet, the development of the great religions of the world, or from a geological point of view the folding up of the Alps, as an outstanding and irrevocable phenomenon. Well, what is happening in front of our eyes today? It is a tremendous and in its kind certainly a unique metamorphosis, which could at best compare with the change which mankind underwent during the dark ages and then again at the beginning of the Renaissance. The world happens to be in the midst of a fundamental change of structure with biological, physiological, sociological and even theological effects, and these are of such profundity that we cannot escape them.
To a certain extent we have been experiencing drastic changes also in our profession. Until recently, our idea of sales promotion moved along perspectives which had already been fixed in medieval times and which were almost exclusively limited to the mere action of selling, and best to a successful sales talk, while today after a short time of transition (calculating just a few years) great value is being placed in an extensive professional erudition, profound psychology, sound argumentation and efficient advice. While previously the old Roman warning Caveat Emptor, which originated from distrust, alerted the buyer to be careful, it now has the meaning that the client wishes to be well informed and accurately advised about the goods he is interested in purchasing. This desire may only be fulfilled by the salesman if he masters a fundamental professional knowledge. Science reigns today over all sequences of our life, medicine a well as commerce, production as well as communication, and the last consumer wishes to share in this professional science.
It is the aim of the gemological courses, which you have so successfully completed, to offer this specialized knowledge which will give you greater self-assurance and consequently increase well founded trust to assist your clients in such a way as to justify the confidence they place in your hands. The relatively broad spectrum of knowledge taught in the condensed form of, say, 25 or 30 assignments distributed over two courses challenged your capability to understand connexions and relationships which exist between different disciplines of the science of nature as well as between different properties of gemstones. The capacity of thinking in relationships and coordinations as well as the readiness to engage yourselves and to take responsibility and to accept solidarity should, apart from your technical achievement, be the human or spiritual benefit of your gemological study. In this sense, I wish to congratulate your most cordially on your successful attainment, which is the well deserved result of your perseverance and brave sacrifice during two years of intensive study. Not only your personal interest in gemology has led you to this award but also your thirst for knowledge and education, that marvelous, growing, aching process, whereby the mind develops into a usable instrument with a collection of proved experiences from which to function.
Some of you may consider the diploma examination as the climax of your gemological studies. Yet, may I bring to mind that this is rather the first ‘rung of the ladder’—that you have merely just crossed the threshold of a space spreading before you with no visible horizon, and the heady sensation you may feel now is only the beginning of further studies combined with unexpected experiences which perhaps are more closely linked with your practical everyday life in future. Therefore I recommend you to remain abreast of future developments by joining the advanced post diploma courses and subscribing to gemological periodicals.
Your diploma should not mislead you to consider yourselves as infallible experts. Your status quo is comparable to the situation of a young B.Sc or Ph.D who has just received his academic title, which does not attest him yet as a fully fledged scientist but merely that he has learnt to think and act independently and—as is to be hoped—with a sense of responsibility.
Among the resources offered to the modern science of nature gemology assumes a prominent place. Unfortunately it was considered a superfluous appendage and hardly acknowledged for almost a generation, and gemological publications only appeared as foot notes to mineralogical literature. Yet, indeed, as an independent basis, gemology has often supplied mineralogy with fundamental data and proved to be of invaluable assistance. Gemology was lacking professionalism for a long time and for far too long gemology was merely a trade accessory. Gemological degrees at present are still no more than school degrees, either rewarded by trade associations or by private institutes affiliated with the trade. An academic degree course would help in upgrading the profession’s standing similarly as university training would facilitate gemology and gemologists to meet the increasing technology and standard of investigation.
However, thanks to numerous outstanding achievements in highly scientific gemological research, today gemology is fully recognized as a science. As a matter of fact, gemology is today rightly entitled to claim the merit of having essentially contributed towards the astonishing progress of mineralogical research. The endeavor to expand as far as possible the boundaries within which may be possible, is a central motive of technical and scientific development. It is the same force which led our progenitors to master the use of fire and which drives us today to investigate outer space without knowing where this may lead us to. This intense desire of mankind to question all boundaries again and again is already grappled in the Genesis of the Old Testament by the words ‘Conquer the Earth with all that is within’ and thus deprived of any further argumentation. However, if man conquers the Earth, then he must corroborate by his mental disposition as well as by his moral conduct that he is indeed legitimized for this role—not only a scientist but also in his quality as a human being.
By this I mean to emphasize that we have a right to profit from our knowledge to our own personal advantage, yet never to use it to the harm of others. A French philosopher expressed this thought with the following word: ‘Science sans conscience n’est que ruine de l’ame’—science without conscience is the undoing of one’s soul. Scientific research means searching for the truth. Consequently, we are obliged to be honest and always tell the truth, and if we happen to make a mistake we should summon the courage to admit it.
Irrevocable laws do not only exist in the field of the sciences of nature but also in the sphere of human life and coexistence. In this connexion I may refer to the problematics of liberty and restraint, to all the tensions which occur because man is a personality who must develop in freedom, yet according to the laws of nature he is also a social being, who can only completely unfold himself in a society. It may not be superfluous to remind ourselves of this fact today, when sometimes righteously, but more often with no right whatsoever, scientific or social achievements are assaulted and when the behavior of certain unscrupulous people assumes a most aggressive character. The essence of the intrinsic virtue of the thing stipulates a much more positive and courageous mind, in social, public, religious and scientific domains, in order to defend all these accomplishments of mankind and save them for future generations.
In this sense I bid you a successful future resulting from your freshly acquired gemological knowledge; may many interesting tests be the source of personal satisfaction and happiness to you and the reason of increasing confidence placed in you by your clientele.
Azurite
Chemistry: Copper carbonate.
Crystal system: Monoclinic; short dense crystals; prismatic, often as spherical radiating groups or botryoidal masses.
Color: Semi-translucent to opaque; dark blue to violetish blue; some transparent crystals.
Hardness: 3.25 - 4
Cleavage: Perfect; Fracture: conchoidal to uneven, brittle.
Specific gravity: 3.7 – 3.9
Refractive index: 1.730 – 1.838; Biaxial positive; 0.108
Luster: Vitreous to waxy
Dichroism: Light blue/dark blue
Occurrence: Secondary ore of copper; found in oxidized portions of copper veins; France, S.Africa, USA, Australia, Russia.
Notes
Unstable. Usually found in conjunction with malachite ‘azurmalachite’; tough variety is called ‘royal gem azurite’ (Las Vagas, USA); effervesces with acid (hydrochloric acid).
Crystal system: Monoclinic; short dense crystals; prismatic, often as spherical radiating groups or botryoidal masses.
Color: Semi-translucent to opaque; dark blue to violetish blue; some transparent crystals.
Hardness: 3.25 - 4
Cleavage: Perfect; Fracture: conchoidal to uneven, brittle.
Specific gravity: 3.7 – 3.9
Refractive index: 1.730 – 1.838; Biaxial positive; 0.108
Luster: Vitreous to waxy
Dichroism: Light blue/dark blue
Occurrence: Secondary ore of copper; found in oxidized portions of copper veins; France, S.Africa, USA, Australia, Russia.
Notes
Unstable. Usually found in conjunction with malachite ‘azurmalachite’; tough variety is called ‘royal gem azurite’ (Las Vagas, USA); effervesces with acid (hydrochloric acid).
Gemmology On A Shoestring
(via The Journal of Gemmology, Vol.10, No.3, July 1966) B W Anderson writes:
It is a worthwhile exercise to make a list of all those gem materials which you believe you can confidently identify by lens inspection only—provided the specimens are clean, not too small, and that the lighting in good. The following list of ‘recognizable’ gems would probably be agreed to by most experienced gemologists, and could, I am sure, be extended: diamond, zircon, demantoid, peridot, opal, amethyst, star sapphire and ruby, chrysoberyl cat’s eye, quartz cat’s eye, iolite, tourmaline, hematite, marcasite, lapis lazuli, ‘Swiss’ lapis, aventurine quartz, bloodstone, ivory, pearl, pink pearl, cultured pearl, imitation pearl, paste, ‘goldstone’, doublets, synthetic star stones, synthetic rutile, strontium titanate, blue sinter spinel. Such a list of thirty materials at least makes an encouraging start; I shall suggest later the basis on which some of the above determinations may rest, and a few simple accessories which may make these and further identifications more simple and more sure.
That the stone examined should be clean (and here I am not referring to inner cleanliness) was stipulated just now, and it is certainly well worthwhile before examining a stone or stones to do a thorough job of cleaning. This is usually quite a simple matter in water containing a little liquid detergent, using soft toothbrush to get into any nooks and crannies of the setting if the stones are mounted. If the stones are then rinsed and shaken, and placed on blotting paper close below the bulb of a desk lamp, they will soon dry. Loose stones, if large, can be handled most safely in the fingers. With small stones, tongs are necessary: these should not be too sharp-nosed, and should have a mild spring. Those who have difficulty in maintaining the correct gentle pressure on the tongs to grip the stone safely while it is being examined may find tongs fitted with a ‘slide’ helpful, as these maintain a fixed pressure. An adjustable desk lamp with an opaque shade is a virtual necessity, enabling a strong light to shine on the specimen without dazzling the eye of the observer. In using a lens, a light interlocking of the left hand holding the specimen and the right hand holding the lens is essential to maintain steadiness and constant focus.
Let us now consider some of the main attributes which enable gemstones to be recognized for what they are.
Color
This is unquestionably the greatest aid of all, though of course it can sometimes be misleading. An attempt to sort out a parcel of mixed colorless stones will soon convince the skeptic how helpful color can be. The gemologist must also be on the look out for parti-coloration, as in many tourmalines; zoned or patchy color as in amethyst, ‘burnt amethyst’, sapphire; dichroism or change of color with direction as in ruby, tourmaline, andalusite, iolite, aquamarine.
Luster
This depends, of course upon the refractive index, but also upon the perfection of polish, which in turn depends largely upon hardness. The polished surface of a diamond will reflect 17% of a ray of light at perpendicular incidence, whereas quartz under the same conditions reflects only 4½% of light. Stones of intermediate refractive index, of course, reflect to extents between these two extremes, in accordance with Fresnel’s well-known formula. The luster of a diamond is certainly one of its outstanding characteristics, and luster can often play a part in distinguishing between similar gems, e.g. between chrysoberyl cat’s eye and quartz cat’s eye.
Fire
The gemologist will know that the effect known as ‘fire’ depends upon the ‘dispersion’ of a stone, which can be stated numerically as the difference between its refractive index for red light of chosen wavelength and for a chosen wavelength of violet light. Fire is most necessary in a colorless stone, if it is to have any beauty and liveliness. Diamond, of course, is our standard here, though considering its high index of refraction its dispersion is decidedly low. By comparison synthetic rutile and even strontium titanate seem to show a rather gaudy display of flashes of spectrum colors. Demantoid garnet owes its lively appearance both to its high luster and its fire: these features should serve to distinguish it at once from either emerald or peridot, even if its color did not. Although the dispersion of synthetic white spinel is only a little higher than that of white sapphire, it does show perceptibly more fire and this makes it a more plausible substitute for diamond, particularly in step cut form.
Transparency
This is contributory factor in the appearance of gemstones which is insufficiently appreciated. Most of the stones used in jewelry would be listed as ‘transparent’, and this would be true insofar as one could read print through a polished block of the stones concerned. But perfect transparency is possessed by very few minerals—diamond, synthetic spinel, and white topaz amongst them—while others, such as zircon, are almost always marred by a slight touch of milkiness. Perfect transparency is, of course, more important in colorless than in colored stones.
Double Refraction
The detection of double refraction in transparent gemstones, and the approximate assessment of its strength, are matters of prime importance in the lens identification of a given specimen, and it is here that a gemologist should score heavily over his unscientific colleagues. The ‘doubling of the back facets’ when viewed through the front of a stone with a lens is very easily in zircon (double refraction 0.06) and sphene (0.13), also in peridot (0.036) and even tourmaline (0.02): but one may need considerable skill in detecting it in quartz and in topaz (0.01, approx.) unless the stone be a large one. It is very important to remember that in all doubly refracting stones there are either one or two ‘optic axes’ along which no double refraction can be observed, and that at right angles to these directions the doubling cannot be seen either, since one image is directly behind the other. Thus one must turn and twist the stone, peering through it at the further facet junctions in all possible directions before deciding whether or not D.R is present, and if so, approximately how strong. Naturally, the larger the stone the greater the effect, and this must be taken into consideration in any assessment made.
Gemmology On A Shoestring (continued)
It is a worthwhile exercise to make a list of all those gem materials which you believe you can confidently identify by lens inspection only—provided the specimens are clean, not too small, and that the lighting in good. The following list of ‘recognizable’ gems would probably be agreed to by most experienced gemologists, and could, I am sure, be extended: diamond, zircon, demantoid, peridot, opal, amethyst, star sapphire and ruby, chrysoberyl cat’s eye, quartz cat’s eye, iolite, tourmaline, hematite, marcasite, lapis lazuli, ‘Swiss’ lapis, aventurine quartz, bloodstone, ivory, pearl, pink pearl, cultured pearl, imitation pearl, paste, ‘goldstone’, doublets, synthetic star stones, synthetic rutile, strontium titanate, blue sinter spinel. Such a list of thirty materials at least makes an encouraging start; I shall suggest later the basis on which some of the above determinations may rest, and a few simple accessories which may make these and further identifications more simple and more sure.
That the stone examined should be clean (and here I am not referring to inner cleanliness) was stipulated just now, and it is certainly well worthwhile before examining a stone or stones to do a thorough job of cleaning. This is usually quite a simple matter in water containing a little liquid detergent, using soft toothbrush to get into any nooks and crannies of the setting if the stones are mounted. If the stones are then rinsed and shaken, and placed on blotting paper close below the bulb of a desk lamp, they will soon dry. Loose stones, if large, can be handled most safely in the fingers. With small stones, tongs are necessary: these should not be too sharp-nosed, and should have a mild spring. Those who have difficulty in maintaining the correct gentle pressure on the tongs to grip the stone safely while it is being examined may find tongs fitted with a ‘slide’ helpful, as these maintain a fixed pressure. An adjustable desk lamp with an opaque shade is a virtual necessity, enabling a strong light to shine on the specimen without dazzling the eye of the observer. In using a lens, a light interlocking of the left hand holding the specimen and the right hand holding the lens is essential to maintain steadiness and constant focus.
Let us now consider some of the main attributes which enable gemstones to be recognized for what they are.
Color
This is unquestionably the greatest aid of all, though of course it can sometimes be misleading. An attempt to sort out a parcel of mixed colorless stones will soon convince the skeptic how helpful color can be. The gemologist must also be on the look out for parti-coloration, as in many tourmalines; zoned or patchy color as in amethyst, ‘burnt amethyst’, sapphire; dichroism or change of color with direction as in ruby, tourmaline, andalusite, iolite, aquamarine.
Luster
This depends, of course upon the refractive index, but also upon the perfection of polish, which in turn depends largely upon hardness. The polished surface of a diamond will reflect 17% of a ray of light at perpendicular incidence, whereas quartz under the same conditions reflects only 4½% of light. Stones of intermediate refractive index, of course, reflect to extents between these two extremes, in accordance with Fresnel’s well-known formula. The luster of a diamond is certainly one of its outstanding characteristics, and luster can often play a part in distinguishing between similar gems, e.g. between chrysoberyl cat’s eye and quartz cat’s eye.
Fire
The gemologist will know that the effect known as ‘fire’ depends upon the ‘dispersion’ of a stone, which can be stated numerically as the difference between its refractive index for red light of chosen wavelength and for a chosen wavelength of violet light. Fire is most necessary in a colorless stone, if it is to have any beauty and liveliness. Diamond, of course, is our standard here, though considering its high index of refraction its dispersion is decidedly low. By comparison synthetic rutile and even strontium titanate seem to show a rather gaudy display of flashes of spectrum colors. Demantoid garnet owes its lively appearance both to its high luster and its fire: these features should serve to distinguish it at once from either emerald or peridot, even if its color did not. Although the dispersion of synthetic white spinel is only a little higher than that of white sapphire, it does show perceptibly more fire and this makes it a more plausible substitute for diamond, particularly in step cut form.
Transparency
This is contributory factor in the appearance of gemstones which is insufficiently appreciated. Most of the stones used in jewelry would be listed as ‘transparent’, and this would be true insofar as one could read print through a polished block of the stones concerned. But perfect transparency is possessed by very few minerals—diamond, synthetic spinel, and white topaz amongst them—while others, such as zircon, are almost always marred by a slight touch of milkiness. Perfect transparency is, of course, more important in colorless than in colored stones.
Double Refraction
The detection of double refraction in transparent gemstones, and the approximate assessment of its strength, are matters of prime importance in the lens identification of a given specimen, and it is here that a gemologist should score heavily over his unscientific colleagues. The ‘doubling of the back facets’ when viewed through the front of a stone with a lens is very easily in zircon (double refraction 0.06) and sphene (0.13), also in peridot (0.036) and even tourmaline (0.02): but one may need considerable skill in detecting it in quartz and in topaz (0.01, approx.) unless the stone be a large one. It is very important to remember that in all doubly refracting stones there are either one or two ‘optic axes’ along which no double refraction can be observed, and that at right angles to these directions the doubling cannot be seen either, since one image is directly behind the other. Thus one must turn and twist the stone, peering through it at the further facet junctions in all possible directions before deciding whether or not D.R is present, and if so, approximately how strong. Naturally, the larger the stone the greater the effect, and this must be taken into consideration in any assessment made.
Gemmology On A Shoestring (continued)
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