The company said the diamond of “exceptional quality” in terms of both its colour and clarity, will be showcased in Antwerp, Dubai, Hong Kong and New York.
Petra, which anticipates that the diamond will be sold via a special tender, said that biddings via its online platform will close on July 12.
While it didn’t set a price range for the stone, the miner said high-quality blue diamonds like the one for sale usually fetch the highest values.
Petra’s Blue Moon of Josephine diamond, cut from a 29 carat rough blue diamond, sold for $48.5 million in 2015.
The figure corresponds to a price of $4 million per carat, which remains the world record price per carat ever paid for a diamond.
Cullinan is known as the world’s most important source of blue diamonds, as well as being the birthplace of the 3,106-carat Cullinan diamond, which was cut to form the 530-carat Great Star of Africa. The operation also yielded the 317-carat Second Star of Africa. They are the two largest diamonds in the British Crown Jewels.