Rio Tinto Group (ASX:RIO) completed the due diligence under the terms of the joint development agreement with Calix (ASX:CXL) for the Zesty Green Iron Demonstration Project, according to a Monday Australian bourse filing by CXL.

The completion of due diligence clears the way for the first cash contribution from Rio Tinto of AU$3 million to the project.

Rio shares fell 1% while CXL shares were up almost 9% in recent Monday trade.