BlueRock Diamonds has recovered a 58.6-carat rough stone at its Kareevlei mine in South Africa, the company’s largest to date.

The stone is a D-color makeable — meaning it is suitable for having one large polished diamond cut from it — so the selling price will likely be “significant,” said CEO Mike Houston in a Monday statement. He added, however, that it contained spotted black sulphide intrusions.

“The final value [will be] dependent upon the buyer’s confidence of what cut stones can be recovered,” Houston explained.

The discovery of the diamond — which will go on sale at BlueRock’s August tender — supports the company’s belief that Kareevlei can deliver high-value stones in addition to its regular, run-of-mine goods, the executive asserted. Parcels of the standard material have sold for more than $400 per carat this year.