Historically, blue diamonds originated from the Kollur mines near Golconda in the Indian state of Hyderabad. It is here that important stones such as the Hope Diamond and the Tereschenko were mined. Most of what is known about early mining activity in India comes through the 17th century traveler and one of the premier gem-merchants of his time, Jean-Baptiste Tavernier.
Tavernier's main client was Louis XIV and he sold to the King a very large blue diamond known as the French Blue which is thought to have yielded the Hope; it is here that the history of blue diamonds began. These Indian deposits have now been worked out and so nearly all the blue diamonds that appear on the market today come from the Premier Mine near Pretoria in South Africa. Natural blue diamonds are among the rarest of colored diamonds and their color comes from the presence of minute amounts of the element boron incorporated within the crystal lattice of the stone during its crystallization process, occurring over 100 million years ago. They belong to an extremely rare Type IIb category of diamonds and are semi-conductors of electricity; an attribute which makes them unique amongst other diamonds.
The 6.21 carats marquise-cut blue diamond featured in Mrs. Kelly's collection has been mounted as a ring by David Morris and further enhanced by two pear-shaped purplish-pink diamonds, showcasing a unique color combination coupled with beautiful workmanship.