The closely guarded sale of the Ekati Spirit is a secret no more.

The 78-carat, gem quality specimen, is widely reported as having sold for $2.8m at auction in Antwerp, Belgium earlier this week.

It has been called Canada's finest diamond but although the price is now clear, the identity of the investor who bought the wonderful piece, and their intentions for it, remain a mystery.

The Ekati Spirit is currently in a rough cut form, leading many experts to wonder if the diamond will remain in its entirety or if the buyer will split it up in the hope of extra profit.

The rock was discovered last year in the wilds of northern Canada at BHP Billiton's Ekati mine, near Yellowknife.

$2.8m of rough Canadian diamond

Prior to the sale BHP Billiton called the 21 x 18 x 13mm diamond "the most significant gem quality diamond to be discovered" at its mine since excavations began in 1998.

The company's biggest success prior to this was a pear-shaped 10.22-carat gem which realised $1.2m.

The company states that the name Ekati Spirit "represents the people of the North, the communities in which we operate, and those who have helped define our distinguished history."