Diamonds are classified into two fundamental groups based on the relative presence or absence of nitrogen incorporated into the crystal structure, as determined by the infrared spectrum.
Type I diamonds contain appreciable concentrations of nitrogen, whereas
Type II diamonds are chemically very pure and do not reveal infrared absorption characteristics related to nitrogen.
A further separation of these two groups includes:
Type Ia (nitrogen atoms present in pairs or groups)
Type Ib (isolated nitrogen atoms)
Type IIa (no measurable traces of nitrogen) and
Type IIb (traces of boron).
"Golconda" is a historic term which refers to diamonds exhibiting an antique cutting style as well as a superior quality. They are very rarely encountered in the gem trade today. In addition, they have properties typical of type IIa natural diamonds (a chemically very pure type of natural diamond). They display the best colour and degree of transparency among all diamonds.
Source: Gubelin Gem Lab
The Golconda diamond mines are located in south central India in what today is the state of Hyderabad. This region was the first known source for rough diamonds from approxiamtely the 4th century B.C. until 1730 when diamonds were discovered in Brazil.
The defining characteristics of Golconda diamonds and what sets them apart and in a class by themselves are their incredible transparency, "whiteness", and purity.
Both the Gemological Institute of America (GIA) and the world reknowned Gubelin Gem Lab characterize diamonds displaying the finest white color and transparency as type IIa, signifying that they are free from nitogen and are therefore chemically pure and colorless.
The term "Golconda" has come to define diamonds of the finest white color and transparency.
Golconda's are extremely expensive. Collectors go mad for Golconda type diamonds.
Type IIa " D " colour diamonds have fetched over twice the normal market value of similar Type I " D " colour diamonds.
Golconda diamonds are very, very rare in today's market and if you do come across one it will usually be at a Christie's or Sotheby's auction.
2002 - On May 15, Christie’s is offering the 75.51 carat D-IF Golconda “Briolette of India,” which is estimated to bring $6-$7 million (or up to $93,000 per carat), as the signature piece of its Geneva sale.
2006 - Christie's Asia in Hong Kong : April 20, A pear-shaped D colour, IF “Golconda” diamond of 13.53 cts US$1,238,640, (US$91,000 per ct.)
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India's Diamonds of Golconda
Diamonds were discovered in India during the 4th century B.C., and India was one of the first countries to mine the gem. India's diamonds were prized for their size and beauty for hundreds of years. "Indian" diamonds were mined in numerous locations that included Borneo (Landak), Golconda, Hindostan, and Raolconda. The majority of India and Borneo's diamond deposits were alluvial as opposed to kimberlite.
India's most prized diamonds are known as the "diamonds of Golconda," and the most famous Golconda stones include the Hope Diamond, Koh-i-Noor Diamond, Orlov Diamond, and Sanc Diamond. The Darya-i-Nur (Sea of Light) was a rare blue-diamond weighed 186 carats, which was owned by the Nadir Shah of Persia after it was plundered from the last 'Great Mughal Emperor,' Aurangzeb's heirs in the 'sack of Delhi' in 1739.
Geology
Millions of years of erosion caused by rainfall and snow-melt, unearthed the diamonds from their kimberlite source, and washed them downstream to their final resting place in the alluvial river gravels of the 'Golconda' region.
Golconda (golkunda) was a region located between the lower reaches of the Godavari and Krishna rivers, in the present-day state of Andhra Pradesh, central India (map above). Today, the exact source of the 'lost mines of Golconda' are unknown, and the India's only remaining diamond source is the Majhgawan pipe near Panna .(see:" Mining in India Today" below).
Diamonds are inextricably woven into the cultural fabric and mysticism of Buddhism, Hinduism, and Tibetan Lamaism. The 'dorjes' is an ancient Buddhist talisman shaped like a pyramidal four-faceted diamond representing the sacred mountain of Mount Meru at the 'center of the universe.'
The 'Valley of Diamonds'
No doubt, many a young lad was drawn to India and the Far East, by tales of adventure and riches beyond one's wildest dreams. The tales of Sinbad and the 'Arabian Nights', were derived from an 8th century Sassanid Persian book called Hazar Afsanah or "Thousand Myths."
In the 'Second Voyage of Sinbad,' he was transported by a giant bird (roc), to a land where the floor of the valley is "carpeted with diamonds." Merchants harvest the diamonds by throwing chunks of meat into the valley, where the birds carry them back to their nest, ladened with diamonds. Sinbad straps one of the pieces of meat to his back, and returns to Baghdad with a fortune in diamonds.
Goa's Diamond Trade Route
Most of the diamonds entering Europe originated in India. In the later half of the 14th century, the diamond trade route extended from India to Bruges, Paris and eventually to the diamond bourses of Antwerp, Belgium. After Portuguese explorer Bartolomeu Dias' 1488 discovery of the 'Cape of Good Hope' on Africa's southern most tip, fellow Portuguese navigator Vasco da Gama discovered a sea route to the India and Orient by sailing around the Cape in 1498. This provided Europeans with an easier route to the Indian diamond trade, avoiding the costly and dangerous 'Silk Road' caravan routes.
Along India's Malabar Coast, the state of 'Goa' grew into a Portuguese trading center, and a diamond-trading route was established from Goa to Lisbon, Portugal and on to Antwerp. In 1510, the Portuguese established a permanent settlement in Velha Goa (Old Goa), after Portuguese admiral, Afonso de Albuquerque defeated the ruling Bijapur kings. The city of 'Vasco,' named after Vasco-da-Gama, is the state of Goa's largest city.
Jean Baptiste Tavernier's "The Six Voyages" (Les Six Voyages) written in 1679 documented his extensive travels throughout India and the Far-East, in order to to expand the trade in gems, jewellery, and other valuable commodities. In 'The Six Voyages', Tavernier meticulously illustrated many notable Indian diamond cuts.
India was the only major producer of diamonds until the discovery of diamonds in South Africa in 1866. Shortly thereafter the De Beers Diamond Company was founded by Cecil Rhodes.
Mining in India Today
India is no longer a source for rough diamonds. Although most all of India's diamond mines were depleted centuries ago, there is one active diamond mine at Panna in the central Indian state of Madhya Pradesh (above picture). The mine is owned by the National Mineral Development Corporation.
De Beers India is currently prospecting in the Madhya Pradesh region as well as in the sothern Indian states of Andhra Pradesh, Chattisgarh, Karnataka, and Tamil Nadu. The De Beers mining operation will be a joint venture with Hindustan Diamond, be based in Mumbai.
The Descriptive Term 'Golconda'
The term 'Golconda' is still used (or misused) today as an indicator of very high quality diamonds. To justify the 'Golconda' name, diamonds must have a level of transparency and quality found only in rare, chemically pure type-IIa natural diamonds. The term 'Golconda' is also used as a generic term to describe higher quality diamonds with an antique cut.
Source: India's Diamonds of Golconda
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