A blue diamond ring that has never been sold at auction is scheduled to appear at Bonhams Fine Jewellery Sale in London on September 21, artdaily.org reports.

The ring, which is estimated to sell for anywhere from $960,000 to $1.28 million, was commissioned from Bulgari in the 1960s by the seller's father as a gift for his wife. The crossover-style ring is set with two large pear-shaped stones that face away from each other – a 3.72-carat Fancy Vivid Blue diamond and a 3.93-carat D color white diamond – as well as smaller white diamonds on the band.

Bonhams' Director of Jewellery Jean Ghika called the blue diamond ring "an exquisite example of Bulgari's craftsmanship at this period" but noted that the blue diamond was "incredibly rare" in itself.