While Rio declared its offer unconditional, the recent 50c boost that raised its offer to $16.50 per share will only apply if it secures more than 47% of acceptance notifications under its institutional acceptance facility by 7pm on April 6.
Rio is in the running for a 41.04% stake under the acceptances so far.
“Now that the offer is unconditional, I would encourage those shareholders who have not yet accepted to do so as soon as possible to maximise the prospect of all shareholders receiving the increased offer price of $16.50 per share,” Rio Tinto Energy chief executive Doug Ritchie said.
“We look forward to moving quickly in developing Riversdale’s projects. Rio Tinto's experience in infrastructure and developing large projects, combined with our financial capacity, will be important in taking Riversdale's asset base to the next stage of development.”
Tata Steel and Brazilian steelmaker Cia Siderurgica Nacional both recently increased their stakes in Riversdale and collectively hold 44.72% of the company.
Riversdale entered a trading halt yesterday after it received a letter from Rio stating it was in discussions with one of the company’s major shareholders.
Riversdale said it "believes that an outcome of those discussions is likely to emerge during the course of this morning”
Riversdale’s flagship Benga coking coal mine in Mozambique is a joint venture development, with Tata owning 35%.
At full production under stage two development, the Benga mine is aimed to export 6 million tonnes per annum of prime hard coking coal and 4Mtpa of export thermal coal by 2013.
Riversdale is also advancing a prefeasibility study for its nearby and bigger $2 billion Zambeze hard coking coal project, which holds more than 9 billion tonnes of resources.
Last year the company started investigating the long-term possibility that Zambeze could become a 90Mtpa run-of-mine operation.
Riversdale shares are up 1.8% to $16.39 after they were released from a trading halt this morning while Rio’s shares are up 1.5% to $83.51.
