By Brecken Branstrator
This 4-carat pear-shaped fancy intense blue diamond will be the top lot at Bonhams London’s upcoming Fine Jewellery sale.
London--The highlight of Bonhams London’s upcoming fine jewelry sale will be a fancy intense blue diamond weighing 4.03 carats.

Pink and blue diamonds have been dominating the auction scene of late, with a number of them setting auction records, including The CTF Pink and the Oppenheimer Blue.

In fact, colored diamonds have increased in value, on average, by 100 percent over the past decade, with blue stones showing the strongest growth over the past 12 months at 5.5 percent, according to the Knight Frank Luxury Investment Index based on data from the Fancy Color Research Foundation.

When the pear-shaped blue diamond hits the auction block at Bonhams Sept. 20 after having been in a private collection in the U.K. for the past three decades, it is expected to sell for between $1.5 million and $1.9 million.

Meanwhile, the sale will feature 188 additional lots, including a selection of white and colored diamonds, sapphires from Kashmir, Burma and Sri Lanka, signed jewelry from Cartier and Van Cleef & Arpels and the private collection of Anglo-Italian designer Andrew Grima, the largest private collection of jewelry from the designer ever to go to auction.

The No. 2 lot of the sale is a fancy colored diamond brooch featuring a 4.83-carat square step-cut fancy gray-blue diamond with fancy dark brown-greenish yellow step-cut diamonds on either side--weighing 2.51 carats and 2.38 carats, and a suspended pear-shaped fancy pink diamond drop weighing 1.90 carats. It could garner between $834,000 and $1.1 million.

Following this piece is a Kashmir sapphire single-stone ring of 9.61 carats. The octagonal step-cut sapphire has no indications of heating, Bonhams said, and is estimated to sell for between $642,000 and $899,000.

Also among the top lots will be a piece perfect for old-cut diamond lovers: A 4.61 carat old marquise-cut type IIb diamond single-stone ring that could sell for between $102,700 and $128,400.

Bonhams will also be auctioning a number of signed pieces from Cartier as part of its sale.

This includes a pair of Art Deco diamond clip brooches circa 1935, estimated at between $51,300 and $77,000, and, adding more color to the sale, an emerald and diamond bracelet by Cartier. It features a series of alternating step- and octagonal-cut emeralds, accented on both sides by brilliant-cut diamonds, and has a pre-sale estimate of $64,200 to $89,900.

Full details of the lots to be auctioned at Bonhams London September Fine Jewellery sale will be put online at the end of this month.

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