The stone, which was unearthed in March, is the largest discovered in Sierra Leone in almost a half-century and is between the 10th and 15th largest ever found worldwide, experts say.
Sierra Leone authorities told reporters that the massive gem will go up for sale on December 4 at Rapaport Auctions, which specialises in the diamond trade.
The government has pledged to be transparent in the stone’s sale, mindful of the history of cross-border diamond trafficking that fuelled Sierra Leone’s civil war from 1991-2002.
Such “blood diamonds” were often found by enslaved members of the population, who were killed or maimed by rebel groups if they refused to dig.
The 709-carat behemoth was discovered by Emmanuel Momoh, an Evangelical pastor who is also one of hundreds of so-called artisanal miners in Kono, Sierra Leone’s key mining district.
Momoh said he hoped the sale would “improve the lives of the people by providing water, electricity, schools, health facilities, roads and bridges” in the Kono region.
The state expects to collect 15 percent of the sale’s proceeds and a 30-percent income tax.
Sierra Leone had initially looked to sell the diamond at home but the best offer the country received was $7.7 million (6.5 million euros) in April, which the government deemed insufficient.
It then decided to sell abroad. The rough stone was shown in Israel on Monday and Tuesday and will be on display in the Belgian city of Antwerp — one of the world capitals for diamond trading — from October 30 to November 10.
The diamond — known under its official name as the “diamond of peace” — will then be shown at the United Nations in New York, authorities said.
“We are grateful to the pastor for transferring the diamond to the government rather than smuggling it abroad,” presidency spokesman Abdulai Bayratay said.
Conflicts and controversy surrounding “blood diamonds” led the international community to enact a process known as “Kimberley” in 2003, which certifies diamonds as “conflict-free”.