The initial 1.7Bt of indicated resources was set in October, with the latest upgrade increasing these resources by 39% to 2.37Bt.

Riversdale also added 6.68Bt of inferred resources to the hard coking and thermal coal project.

About 68% of the total resources are at depths of less than 500m, 28% is 500-700m down, while 4% is deeper than 750m from the surface.

“The upgrade of total coal resources to over 9 billion tonnes confirms the Moatize Basin’s status as a coal province of global significance,” Riversdale executive chairman Michael O’Keeffe said.

The results were based on 150 boreholes covering 50,000m with coal quality determined by analysis of core from 50 holes with a minimum of 95% core recovery.

The Zambeze project stretches for 24,740 hectares and is next to Riversdale and Tata Steel’s Benga coking coal mine.

Including the 4Bt Benga resource, Riversdale said it is now managing resources of more than 13Bt.

Riversdale said the Zambeze project was considerably larger than Benga but had a similar structure with 22 coal seams outcropping over a 14km strike length across the northern part of the tenement.

Named after the nearby Zambezi River, Riversdale said the project was well positioned to expand infrastructure including power, water, sealed roads and rail.

“Riversdale Mining is in discussions with a number of steelmakers in Asia,

Europe and South America regarding coal sampling and the future marketing of potential coal products,” the company said.

“These products are expected to comprise quality hard coking coal and a secondary thermal coal product, consisting of high-energy thermal coal suitable for both the Indian and African markets.”

The completion of stage one development of Benga to reach 5.3Mt per annum of run-of-mine coal is due in mid-2011 while the stage two feasibility study is targeting 10.6Mtpa of ROM coal by 2014.

Tata Steel owns 35% of the JV and will firm up coking coal supply through Benga.

Riversdale shares closed up 2% to $9.43 yesterday.