"It can be hard to visualise exactly how big a 76.02 carat diamond is," Christie's head of jewellery, Rahul Kadakia, said.
The gem originated from India's now defunct Golconda mine, sharing its origins with some of the world's most impressive diamonds including the Kohinoor, part of the British Royal Collection and the Regent, which is the centrepiece of the French Crown Jewels, the Daily Mail reported.
"It's about the size of a quail's egg, and completely pure and clear in colour," the paper quoted Kadakia as telling Today magazine.
Although it has an estimate of $15 million, experts believe that the diamond will fetch a lot more, attracting buyers from the Middle East, Asia and Russia.
"$15 million is a very fair estimate and we do hope that we will achieve a new record price," Kadakia said.
"If it does go on to make more than $15 million, that is quite a return on investment. In what other type of asset could you expect that kind of return over 19 years?" he added.
The gem is named after its original owner Archduke Joseph August, who was the highest ranking official in the Kingdom of Hungary during the 19th century.