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Golconda...

The Golconda Mystique
Once prized for their mystical powers, diamonds from the Golconda mines of India remain among the most coveted of gems.
By Dr. Eric Erel

Golconda diamonds were mined in the ancient kingdom of Golconda in south central India -- today the state of Hyderabad -- beginning more than 2,000 years ago. For centuries, diamonds from these mines have been prized for their incredible transparency,whiteness and purity. The renown of the Golconda mines also owes much to the fact that a number of the world’s most historically significant diamonds have come from these mines. These stones include the Koh-I-Noor, the Regent, the Great Mogul and the Tavernier Blue, from which the Hope Diamond is believed to have been cut.
Today, true Golconda diamonds are extremely rare and exist mainly in museums or collections of renowned persons like Indian rulers, European kings or rich connoisseurs, who can trace them back to the eighteenth century or earlier. Occasionally, such stones may come up for sale at auction by Christie’s or Sotheby’s but that is a special occasion.
Over time, the term Golconda diamonds has evolved to describe diamonds with the same high level of transparency, clarity and whiteness as the diamonds actually mined in Golconda. Since the 1980s, the Gübelin Gem Lab has issued a Golconda Appendix as an addition to its grading report for exceptional diamonds that show a combination of rare properties, such as an antique cutting style and superior color and clarity. To earn this appendix, these stones also must qualify as type IIa diamonds, signifying that they are free from nitrogen and therefore chemically pure.
To understand the significance of the Golconda descriptive, it is necessary to go back thousands of years to India, the country where diamond mines were originally discovered. As early as 800 B.C., Indian diamonds were collected in secondary deposits. At the end of the thirteenth century, Marco Polo, the renowned Venetian traveler, visited the kingdom of Warangal and described the process of collecting diamonds that took place after heavy rains fell, in the beds of the torrents. Later, mines were also dug underground in ancient alluvial deposits, and diamonds were collected in tunnels and open pits. The legendary French diamond merchant Jean Baptiste Tavernier, who visited numerous Indian diamond mines between the years 1630 and 1668, reported that as many as 60,000 persons were working in the mines at any one time.

The Magic of Golconda
Mysticism and other magical powers were always associated with diamonds in the culture of India. Diamonds were seen as talismans and were believed to contain powers derived from the gods. For the transfer of beneficial influences -- such as happiness, wealth, prosperity or children -- to occur, the persons possessing diamonds were required to meet certain qualifications of rank and status. Only kings and priests, for example, were allowed to possess the pure, colorless Golconda diamonds.
Since the earliest times, the quality criteria for diamonds were mainly correlated to their shape, color and clarity. An ideal diamond crystal had to possess a perfect octahedral form, to be free of any blemishes and to be perfectly white. Such a diamond crystal, like the prism, has the power to create the “magic” rainbow by dividing the sunlight into all the spectral colors. This important optical property was associated with talismanic forces. Mystical interpretations say that only a rough diamond possesses beneficial virtues. That explains why, when diamonds were set in jewelry before the fourteenth century, they were usually in their natural shape.

Origins of Cut
The earliest evidence of cutting -- polishing and cleaving -- dates to the fourteenth century and appeared at the same time in India and in Europe. The point cut, which resembles a four-sided bipyramid, is believed to be the first diamond cut. This cut, which remained popular until the Renaissance period, improved the shape of natural octahedral crystals into a more perfect form.
The next to appear was the table cut, obtained by the truncation of one point with a polished and flat surface called the table. Sometimes a lower point could also be cut out in order to add a small culet. This cutting style dominated from the end of the fifteenth century until the seventeenth century. During that period, many point cut stones were recut into table cuts.
The third cutting style, introduced in the sixteenth century, was the rose cut. This cut, characterized by a flat bottom and a domed front with triangular facets, was immensely popular until the nineteenth century. Other cutting styles that appeared between the fifteenth and the sixteenth centuries simply added facets to table cut stones.
At the beginning of the seventeenth century, the Mazarin cut was developed, named after Cardinal Jules Mazarin of France, who lived from 1602 to 1661. This cushion-shaped diamond was one of the earliest faceted cuts and contained 34 facets. Following the Mazarin cut, the brilliant cut, known as the old mine cut today, was introduced. It contained 58 facets, the same as the modern brilliant. More conical shapes with rounded outlines were also cut and called brilliant cut. The brilliant cut was popular from the middle of the seventeenth through the eighteenth century and many previously cut diamonds were recut in this style in order to modernize them. By the nineteenth century, the shapes became more rounded and, at the beginning of the twentieth century, the modern round brilliant appeared.
From antiquity until the eighteenth century, diamonds were very rare and most of them originated in India. However, beginning in the eighteenth century, this situation changed dramatically with the discovery of diamonds in Brazil in about 1730 and in Africa, in about 1870. Today, diamonds are extracted in many countries and, due to the absence of criteria for geographic origin, it is impossible to determine where specific individual diamonds were mined.

Identification
The typical Golconda shapes are table cut and the succeeding, more faceted cuts in use until the eighteenth century, including cushion, oval, old pear and marquise shapes with rounded ends, as well as other shapes with irregular outlines. These antique cuts usually display, among other criteria, a high crown, large culet, numerous and irregular extra facets and both naturals and indented naturals that remain from the original surface of the rough.
According to modern grading systems, these stones would be characterized by a low polish and symmetry grade, and often with a low clarity grade as well. Due to the cutting techniques between the fourteenth and eighteenth centuries, when it was impossible to get a perfectly polished and symmetric diamond, the presence of flaws near the surface had more to do with the quality of the finish than with the clarity of the diamond. For this reason, a Golconda Appendix does not necessarily indicate a flawless or internally flawless (IF) stone. Diamonds with lower clarity grades, which can become IF after a minor recutting, are also eligible for this appendix.
In terms of color, only colorless diamonds with a D color grade are eligible for the Golconda Appendix, as well as certain fancy colors exhibited by one of the historical Golconda diamonds, such as the blue Hope or the pink Grand Condé.
The last criteria for the Golconda Appendix are related to the size and type of the diamond. The appendix is restricted to type II diamonds only because most of the large, historical Golconda diamonds are type IIa stones and because type II diamonds are very rare.
For the Gübelin Gem Lab, the Golconda Appendix is designed to reflect the high quality and rarity of the large and historical diamonds that originated in India’s Golconda mines. This appendix is delivered very rarely and only for exceptional diamonds, whatever their geographical origin, in accordance with the quality criteria seen in India thousands of years ago and the properties known to be typical of the famous Golconda diamonds.
Dr. Erel is a gemologist with the Gübelin Gem Lab in Lucerne, Switzerland.
Article from the Rapaport Magazine - January 2009.