It was about ten years ago, at a jewelry show, when I first came across a Golconda diamond. I had never seen one before, but I will never forget how that single diamond was the shiniest and most translucent diamond among all others displayed!
I’ve been lucky enough to have seen a few Golconda diamonds, as they are extremely rare. Golconda diamonds come from the Golconda mine in India. The mine is no longer functional, in fact it ran dry more than 200 years ago. It’s a ruined city of Southern India and capital of ancient Golconda Sultanite ( c. 1518 – 1687 ). The mines in this region have produce the world’s most beautiful and famous gems, including The Hope Diamond and The Kohi-Noor.
What’s so special about the Golconda diamonds was the absence of chemical impurities. These impurities are not same as inclusions which diamonds are graded for example VVS, VS, SI, etc.. These impurities are measured at the atomic level within the crystal lattice of carbon atoms. So unlike inclusions, impurities require an infrared spectrometer to detect.
In order to understand this, it’s helpful to know that scientifically diamonds are separated into 4 types based on their chemical impurities: Type Ia, Type Ib, Type IIa, and Type IIb. Type Ia diamonds make up about 98% of all natural diamonds. The nitrogen impurities are about 0.3%. Type IIa diamonds make up 1 – 2% of all natural diamonds. There are almost, and sometimes, no impurities (nitrogen) and consequently are colorless and very transparent! Type II diamonds were formed under extremely high pressure for longer time period.
Here’s an image of a 52 carat Golconda diamond that will be auctioned at Christie’s New York. It’s expected to fetch between $9.5 million to $12.5 million!!