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Pretty in pink: How origin reports for pink diamonds may affect their value

Golconda diamonds

Underground mining at Argyle will extend the mine's life by another seven years.
Underground mining at Argyle will extend the mine’s life by another seven years.

Historically, there are diamonds that command higher prices simply due to their specific origin. Golconda stones are one example. Sourced from a geographical area in India of the same name, these diamonds are of the Type IIa variety, which accounts for less than two per cent of the world’s diamonds.

Today, authentic Golconda diamonds are extremely scarce and are found mainly in museums or in collections with roots going back to the 17th century. Occasionally, such stones with a provenance letter from a recognized lab may come up at auction, but that happens rarely.

Over time, the term ‘Golconda’ has evolved to describe diamonds with the same high level of transparency, clarity, and colour (known in the trade as ‘D plus’). Since the 1980s, the Gübelin Gem Lab has issued a Golconda Appendix as an addition to its grading report for “exceptional diamonds that show a combination of rare properties, such as an antique cutting style, as well as superior colour and clarity. These stones also must qualify as Type II diamonds, free from nitrogen and therefore chemically pure.” A small percentage of them are also blue or light pink in colour.

The rarity of pink diamonds

The author with Adolf Peretti of Gem Research Swisslab (GRS) at the Argyle mine earlier this year.
The author with Adolf Peretti of Gem Research Swisslab (GRS) at the Argyle mine earlier this year.

Blue and pink diamonds (especially when they are saturated enough to be graded fancy red) are considered the most expensive natural creation by weight in the world. After India’s major production of diamonds began in the 17th century, Brazil was the next primary source for colourless and coloured diamonds, including rare pink and blue stones originating from the panning of gravel in its rivers.

It was in one such small river that a local boy found a red 13.90-carat diamond crystal while swimming. In 1990, the crystal was purchased by William Goldberg Diamond Corp., and cut to produce a 5.11-carat fancy red, the largest of its kind. In 2001, it was purchased by Moussaieff Jewellers for $1.8 million USD per carat and re-named the ‘Moussaieff Red.’ Originating from approximately one gram of carbon that turned red as a result of a perfect combination of pressure and temperature, the stone is currently valued at more than $9 million USD.

At 59.60 carats, the flawless ‘Pink Star’ was offered at auction for $83 million USD last November. Although it carried a GIA report indicating it is a Type IIa fancy vivid pink, there was no provenance information. Based on our research, Type IIa pink diamonds are generally sourced from India, Brazil, or Africa, and not Australia, Canada, or Russia, as stones from these areas are all Type Ia and contain nitrogen.

The following are known sources of pink and purple diamonds and their claim to fame regarding important stones:

  • India (Golconda—the 28.15-carat ‘Agra’ pink diamond);
  • “¨Brazil (Minas Gerais—the 5.11-carat ‘Moussaieff Red’);
  • South Africa (Premier mine, also the source of blue diamonds; Cullinan mine is a source of large Type IIa diamonds);
  • “¨Tanzania (the 23.60-carat ‘Williamson Pink’);
  • Russia (Siberia—mostly purple diamonds);
  • Australia (Argyle mine—.95-carat ‘Hancock Red,’ first gem to be sold for $1 million per carat); and
  • Canada (Northwest Territories [Diavik mine], some pinkish-purple diamonds; and Northern Ontario [Victor mine], pink).

Pink diamonds appeared only sporadically in jewellery until the discovery of the Argyle mine. In the mid-1980s, it became the first mine ever to produce a steady supply of fine melee (up to .10 carats) and small pink diamonds (less than one carat), along with rare one-carat-plus pinks. The new mine supplied enough volume to make pavé setting possible with pink diamonds.

Since it was commissioned in 1985, Argyle has produced more than 800 million carats of diamonds—less than 0.1 per cent has some pink colouration. To offer some perspective, the entire annual production of pink diamonds greater than .50 carats could fit in the palm of your hand and represent 10 per cent of the value of all Argyle diamonds. The rarest pink and blue diamonds are sold at annual tenders in major cities around the world to a select group of diamantaires.

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