A two stone ring from Italian luxury jeweler BVLGARI with a rare triangular blue diamond once bought as a token of appreciation is up for sale at Christie's auction in New York in October this year. The ring originally bought in 1972 for $1 million by a European businessman for his wife celebrating the birth of his child features the rare diamond the size of a quarter on a gold band with baguette-cut diamonds around it. It is expected to fetch at least $15 million.

According to jewelry expert from Christie's this is the largest triangular-shaped fancy vivid blue diamond at 10.95 carats. The diamond is paired with a 9.87-carat white diamond cut in the same shape. The Gemological Institute of America also claims that this is the largest ever blue triangle diamond ever to be graded, and the vividness of the color is remarkable. Its pair in the ring, the white diamond is equally brilliant though smaller in size.

The ring sports the classic BVLGARI design templates which take from geometric forms, classic Greek and Roman designs and unusual combinations of colored and colorless diamonds. The expert from Christie's explained that the blue diamond has most likely been sourced from the Premier Diamond Mine in South Africa, the only mine in the world producing blue diamonds.