The Toronto-listed company announced a positive preliminary economic assessment for the project overnight, which returned a post-tax net present value of $US533 million and an internal rate of return of 31%.

The redevelopment of the historical mine will focus on the Big Zinc Zone, which has a measured and indicated resource of 10.2 million tonnes grading an eye-watering 34.9% zinc – twice the grade of the next highest-grade global project.

The study envisaged a two-year construction phase for a 10-year mine life producing 530,000t zinc concentrate grading 53% zinc per annum at total cash costs, including copper by-product credits, of 54c per pound of zinc.

Capital costs were put at around half a billion, including contingency.

“This preliminary mine redevelopment plan supports our view that Kipushi is the best brownfield zinc project in the world,” Friedland said.

“Kipushi’s zinc grade of almost 35% puts the project into a class of its own.”

Kipushi was formerly the King Leopold mine when the DRC was a Belgian colony, and was once the world’s richest mine.

Friedland said much of Kipushi’s underground development and infrastructure was already in place.

“The combination of extremely high zinc grades, low capital requirements and low operating costs makes this a compelling development project,” he said.

“In April of this year, zinc inventories dropped to the lowest levels since August 2009, providing a great deal of optimism for significantly higher zinc prices in the next few years.

“As such, we believe that market conditions are ideal as we evaluate the available options to return Kipushi to production.”

Ivanhoe owns 68% of the project, while state-owned Gecamines owns the balance.

The study has been sent to Gecamines for review and approval.