One of the rarest diamonds on earth, this Bulgari two-stone ring is unique for many reasons. However, it's not semi-precious stones which we speak of, but elegant one. Bvlgari Two-Stone Diamond Ring, a stunning two-stone diamond ring designed by the legendary jewelry house in the 1970s. This featuring the largest triangular-shaped fancy vivid blue diamond ever to appear at auction, easily becomes one of the most expensive rings in the world due to the two large diamonds it contains. Created in 1972 from the Bulgari collection, an Asian collector willingly bought the ring for $15.7 million after an intense bidding war.