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Lot Essay
According to a note from the Gübelin Gem Lab accompanying the report,
'Large rubies of top-gem quality are true rarities of nature. Not only is a delicate mineralogical balance essential for this red variety of corundum to be formed deep within the earth, but specific geological conditions as well as precise pressures and temperatures must also be present. Furthermore, the continuous supply of a rare combination of chemical elements, such as aluminium and chromium, are yet another necessity required for the formation of rubies.
Over the past decades, various heating techniques, as well as the use of chemical additives, have been introduced to increase the supply of high-quality rubies. The aim of these treatments was and still is to improve the visual appearance of the gemstones. Prior to the advent of modern heating techniques, rough rubies were cut and polished retaining the quality that nature had originally endowed them with. Therefore, in earlier times, rubies with obvious imperfections were considered and accepted as the norm. However, the expectations with respect to quality (colour and transparency) rose steadily. The demand for natural, high-quality, unheated rubies kept growing while the supply of such gems stagnated.
During the last couple of years, the supply of high-quality rubies decreased even further. Myanmar (Burma) experienced a significant drop in its production of high-quality gemstones. Other producing countries such as Madagascar, Kenya, Tanzania, Vietnam, Afghanistan and Tajikistan, also could not satisfy the demand for top-quality rubies. As a result, large, natural, untreated rubies of almost any geographic origin have become even more difficult to find on the market today.
[This] 10.74 ct ruby possesses a combination of gemmological characteristics which does not permit a sufficiently secure identification of origin. It may be stated, however, that the above mentioned ruby does possess characteristics indicative of rubies which have derived from marble-type deposits, such as those in Afghanistan, Tajikistan or Vietnam. At this moment, it is not possible to classify the probable source any further.'
According to Dr. Jack Ogden of the Gemmological Association of Great Britain,
'Large rubies of good colour are extremely rare. Indeed, even the celebrated Mogok mine in Burma (Myanmar) and the Jegdalek mine in Afghanistan have rarely yielded rubies of good colour that weigh more than about 5 carats when cut and polished.
In some cases a combination of microscopic, analytical and other characteristics will allow a laboratory to attribute a ruby to a particular mine with a high degree of certainty, but many more sources of ruby are known today than in the past, and we also have far greater understanding of the geological context of their creation. Geology has no respect for modern political borders, so in many cases the best that even a major laboratory can do is to describe the origin of a ruby in terms of its geological source type.
The heating of rubies to enhance their colour is a practice that can be documented as far back as Medieval times. The practice is widespread today and thus there can be a major premium for a stone of fine colour that is accompanied by a report from a reputable laboratory that states that no evidence of heat treatment was detected.'
'Large rubies of top-gem quality are true rarities of nature. Not only is a delicate mineralogical balance essential for this red variety of corundum to be formed deep within the earth, but specific geological conditions as well as precise pressures and temperatures must also be present. Furthermore, the continuous supply of a rare combination of chemical elements, such as aluminium and chromium, are yet another necessity required for the formation of rubies.
Over the past decades, various heating techniques, as well as the use of chemical additives, have been introduced to increase the supply of high-quality rubies. The aim of these treatments was and still is to improve the visual appearance of the gemstones. Prior to the advent of modern heating techniques, rough rubies were cut and polished retaining the quality that nature had originally endowed them with. Therefore, in earlier times, rubies with obvious imperfections were considered and accepted as the norm. However, the expectations with respect to quality (colour and transparency) rose steadily. The demand for natural, high-quality, unheated rubies kept growing while the supply of such gems stagnated.
During the last couple of years, the supply of high-quality rubies decreased even further. Myanmar (Burma) experienced a significant drop in its production of high-quality gemstones. Other producing countries such as Madagascar, Kenya, Tanzania, Vietnam, Afghanistan and Tajikistan, also could not satisfy the demand for top-quality rubies. As a result, large, natural, untreated rubies of almost any geographic origin have become even more difficult to find on the market today.
[This] 10.74 ct ruby possesses a combination of gemmological characteristics which does not permit a sufficiently secure identification of origin. It may be stated, however, that the above mentioned ruby does possess characteristics indicative of rubies which have derived from marble-type deposits, such as those in Afghanistan, Tajikistan or Vietnam. At this moment, it is not possible to classify the probable source any further.'
According to Dr. Jack Ogden of the Gemmological Association of Great Britain,
'Large rubies of good colour are extremely rare. Indeed, even the celebrated Mogok mine in Burma (Myanmar) and the Jegdalek mine in Afghanistan have rarely yielded rubies of good colour that weigh more than about 5 carats when cut and polished.
In some cases a combination of microscopic, analytical and other characteristics will allow a laboratory to attribute a ruby to a particular mine with a high degree of certainty, but many more sources of ruby are known today than in the past, and we also have far greater understanding of the geological context of their creation. Geology has no respect for modern political borders, so in many cases the best that even a major laboratory can do is to describe the origin of a ruby in terms of its geological source type.
The heating of rubies to enhance their colour is a practice that can be documented as far back as Medieval times. The practice is widespread today and thus there can be a major premium for a stone of fine colour that is accompanied by a report from a reputable laboratory that states that no evidence of heat treatment was detected.'