The 76-carat Archduke Joseph diamond, described as internally flawless, comes from India's famous Golconda mines.

BBC: 'Perfect' Archduke Joseph diamond sells for $21m

All four of the world's top pink diamonds have been found at Golconda, Christie's says.

BBC: Princie Diamond: Rare Indian gem sells for $39m

These were stored in the fortress at nearby Golconda, seven miles west of Hyderabad.

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The diamond came from the ancient Golconda mines, where the famous Koh-i-Noor and blue Hope Diamond originated.

BBC: 'Perfect' Archduke Joseph diamond sells for $21m

The 34.65 carat diamond's origin can be traced back to the ancient diamond mines of Golconda in southern India.

BBC: Princie Diamond: Rare Indian gem sells for $39m

The Golconda mines, surrounding the ancient ruined city of Golconda in south-central India, were renowned for the diamonds they produced.

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"It could be a real good thing, " says 23-year-old Frank Johnson, who lives in the Pope County seat of Golconda, a shrinking Ohio River town of 670.

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Christie's say that the Princie Diamond is believed to be the third largest pink diamond in the world and was found 300 years ago in the Golconda mines.

BBC: Princie Diamond: Rare Indian gem sells for $39m

"It is a world record for a Golconda diamond and a world record price per carat for a colourless diamond, " Francois Curiel, director of the international jewellery department at Christie's, told reporters.

BBC: 'Perfect' Archduke Joseph diamond sells for $21m