By admin January 01,2017
The diamonds with a strong blue colour (deep blue) are the rarest and most expensive. The lighter the tone the lower the price of the diamond.
A 0.23ct VS1 Cushion Cut Diamond graded as Natural Fancy Light Blue was available on 8th December 2017 for around AUD$18,500.
A 0.21ct VS2 Cushion Cut Diamond graded as Natural Fancy Vivid Blue was available on 8th December 2017 for around AUD$92,000.
The grading of these diamonds is no different to any other diamond.
The 4C’s apply to all diamond varieties whether white/colourless or fancy coloured. The only difference is the colour grading.
The following are taken into consideration when grading the colour:
Hue – the most noticeable colour present;
Saturation – how strong & vivid the colour &
Tone – how dark or light the colour of the diamond is.
Blue diamonds are not as easily available as some of the other fancy coloured diamonds.
These diamonds are extremely rare, rarer then the pink.
The colour is caused by the presence of Boron in its composition.
The Cullinan mine in South Africa is owned by a UK mining company Petra Diamonds Limited and is the largest producer of blue diamonds.
Blue diamonds are divided into eight categories:
Fancy Deep/Fancy Dark
These are then further divided based on their secondary colours.
Argyle and GIA grade blue diamonds differently.
Argyle uses a letter and number colour grading scale whereas GIA colour grades the blue diamonds by listing the intensity of the colour followed by the secondary colours and ending with the most dominant colour. The size and clarity remain the same. Argyle’s colour grading scale ranges from 1 to 3+ with 1 being the lightest blue and 3+ the most vivid.
B1 – Very Light
B2 – Light
B3 – Intense
B3+ – Vivid
A 0.15ct SI1 Round Blue diamond was graded by Argyle as BL2 and by GIA as a Fancy Greyish Blue.
In June 2014 122.52ct blue diamond was recovered and then in September of that year sold uncut for US$27.6million (US$225, 269 per carat)
This diamond was then cut into four diamonds:
7ct Cushion Cut;
10.30ct Radiant cut;
11.3ct Pear shaped and
24.18ct cut-cornered rectangular mixed-cut
This 24.18ct Fancy Intense Blue Diamond known as “The Cullinan Dream” with an estimated value of US$23m – US$29 million, was on display at Christie’s auction on 9th June 2016 in New York and sold for US$25.365 million. This is the largest blue diamond to ever be offered on auction.
Sotheby’s May 2017 Geneva
The Sotheby’s May 16, 2017 Geneva auction had on display the 14.54ct Pear Cut Internally Flawless, largest fancy vivid blue diamond, known as the “Apollo Blue” which was expected to sell for $38 million to $50 million.
Together with the Apollo Blue was the Artemis Pink, a 16ct Pear Cut diamond of VVS2 Fancy Intense Pink, estimated to sell for $12.5 million to $18 million. These two diamonds were sold together to an anonymous buyer for US$57,425,478 (AUD$76,502,439)
Sotheby’s April 2016 Hong Kong
The Sotheby’s April 2016 Hong Kong auction of the DeBeers Millennium Jewel 4, 10.10ct oval internally flawless fancy vivid blue diamond sold for US$31,830,769 ($3,168,643 per carat) to an anonymous telephone buyer.
Sotheby’s April 2016 New York
The Sotheby’s April 2016 New York auction had a Light Blue VS2 Pear shape 5.06ct for $286,561 per carat.
Rough Diamonds from The Cullinan and Williamson Mines in Africa
Both the Cullinan mine and the Williamson mine produce a range of diamonds of various quality and colour including blue, pink, yellow and champagne.
The rough diamonds are sorted by size, quality (colour and clarity) and then sorted in parcels. The high quality larger stones or coloured stones are sold as single lots usually offered at auction through Sotheby’s or Christies.
Petra has approximately five tenders per year with each one lasting four to six days where the participants view the assortments and place a confidential electronic bid on the parcel of their choice. At the end of each tender, the highest bidder wins the parcel.