The Indian diamond that got the highest price - Archduke Joseph diamond

Archduke Joseph diamond from Golconda, India CBS News
Kingdom of Golkonda, India.
Of all the gem stones known to mankind, diamond is the most admired and revered one. It may be 'Diamonds are a girl's best friends' and it is quite imperative that they are inspiring to fashionable and positive women whose beauty is enhanced when they wear it. When such women go to parties wearing dazzling and resplendent diamond ornaments, it is needless to say they leave a glittering and  bright swathe behind them, making eligible young men drop their jaw. However, the underlying drawback is such valuable stones are also a source of irritation to the owners. You get the attention of one hundred pairs of curious eyes of rich gossiping ladies and also one dozen pairs of anxious eyes of diamond robbers, not to speak of the risk of the proverbial curse such diamonds may carry. Considering the transient nature of our life I like what Emma Goldman says about this hardened carbon (see the quote below). 
Brainy Quote
 As far as diamonds are concerned, in the past, most of the world famous ones came from Kollur mines in Golconda, near Hyderabad in the present state of Telengana.  The best open-cast mines were on the banks of the  Krishna river in the present day Krishna and Guntur districts( that formed part of the Golconda Kingdom). Now defunct, once Golconda town was famous for diamond cutting and diamond and gemstone trading as well and had close links with many diamond experts.

The most distinctive feature of Golconda diamonds is  (some experts believed in the past), the presence of less nitrogen or boron  or lack of them  may make them differ  from other diamonds. Yet another feature is they contain less impurity, hence many of them are colorless. Until the end of 19th century, Golconda was a famous diamond center where the industry was involved in important activities related to diamond processing - sizing, cutting, polishing, sorting , marketing, etc., employing 10,000 plus people. The medieval diamond trade here  got the attentions of famous French diamond traders and experts such as  Jean de Thévenot and François Bernier.  According to the Hyderabad (Deccan) based historian, Mohammed Safiullah  the estimated output from all mines in Golconda was believed to be around 12 million carats (vide: The New Indian Express of 22 October 2016). India is the only country where the diamonds have a long history and are said to  have been known for at least 3,000 years but most likely 6,000 years. They were mostly found in placer / Alluvial deposits.

Among the countless famous diamonds from Kollur mines, the following may be worthy of mention:
 Archduke Joseph Diamond, 78.54 carats (15.708 g) cut; auctioned by Christie's in New York and purchased by an anonymous collector.
The Orloff Diamond, 300 carats (60.0 g).  Daryā-ye Nūr, 182 carats (36.4 g); the largest one in the Iranian Crown. The Golconda Diamond, 135 carats (27.0 g); belonging to Dunklings Jewellers, Melbourne, Australia.  Koh-i-Noor, 105.6 carats (21.12 g) (793 carats (158.6 g) rough, 186 carats (37.2 g) cut, further cut for Crown Jewels); in the British Crown Jewels, London. The Hope Diamond, 67 carats (13.4 g); in the American Museum of Natural History, the Smithsonian Institution, Washington and  Wittelsbach-Graff Diamond, 31.06 carats (6.212 g) cut; currently owned by Hamad bin Khalifa Al Thani, former ruler of Qatar.
Archduke Joseph. .
 Among the famous diamonds mentioned above, the rare 76 carat diamond mined from erstwhile Golconda kingdom, named after its first known owner Archduke Joseph August of Austria that had lain unnoticed for a long time, gained overnight popularity. It  was sold for a  whooping record price 
 of €16.9 million (about Rs. 118 crore) at an auction in Geneva in November 2012. The hugest for a diamond so far.  It was sold by American jeweler Black, Starr & Frost  through the auction company.  The successful bidder maintained his  anonymity.  This  sensational auction  by Christie’s drew the attention of connoisseurs of  precious stones  across the globe. As to this diamond's transport to Austria, some confusion still lingers. According to Mr. Narendra Luther, Historian on Qutub Shahi Sultans' in 1893 Archduke Franz Ferdinad was a guest of the 6th Nizam Mahbub Ali Khan at Hyderabad and apparently the Austrian got the diamond from the ruler as a gift. Archduke's son for safety purpose deposited the gem  in the vault of Hungarian General Credit Bank in 1933. After resurfacing in 1961, it ended up in Christie’s Geneva auction house in 1993 where it was sold for $6.48 million.