The name “Golconda” leaves even experienced diamond dealers struggling to describe the beauty and magnificence that these stones exhibit. They are among the whitest and purest diamonds in the world, and are incredibly rare.
The Golconda region is in small corner of India, near the region of Hyderabad. For many years, until discoveries in Brazil in 1730s and later South Africa in the mid-1800s, it was virtually the only source of diamonds in the world. Most diamonds were found in secondary deposits, that is found on river beds, rather than mined. The name is so magical in the diamond world that other places have been called after it, including the Golconda mine in Minas Gerais (Brazil), three towns in America (in Nevada, Idaho and Illinois) and i nTasmania.
To be called a Golconda diamond, the stone has to satisfy two criteria: it must have come from that region, and it must be what is called a type IIa diamond, which means that is has almost no nitrogen present, and is just pure carbon. (Most diamonds contain trace amounts of nitrogen). So not all type IIa diamonds are Golconda diamonds! For this reason, diamond certificates do not have a country of origin of the diamond.
They have an elusive quality, enhanced by the beauty of the old cushion cut that most of them have. It is a soft cushion shape, which brings out all of the radiance of the stone. The biggest appeal of them is the way light moves through the stone; it is as though the light moves through the diamond unimpeded, as if through a vacuum. It is not the same as flawless, it is a purity of reflection that is hard to describe but very easy to recognise.
Many of the world’s most famous diamonds are from Golconda, including the Pitt-Regent diamond (140 carats), the Idol’s Eye (70 carats), the Agra Diamond (28 carats), and possibly the most famous diamond of all, the Hope Diamond.
While it is straightforward for a laboratory to tell what type a diamond is, it is very difficult to know sometimes where a diamond came from, particularly if it is an old diamond. This makes genuine Golcondas very rare in today’s world.