The Tata Steel nominee on the board of Riversdale, Narendra Kumar Misra, abstained from voting on a resolution to announce and recommend the offer to shareholders.
The move follows Rio Tinto Jersey Holdings 2010 Ltd's decision to delist Riversdale Mining Ltd, after the company's shareholding in the mining company increased to 73.20 per cent.
Prior to Rio Tinto's $3.9-billion offer for Riversdale in December 2010, Tata Steel had 24.4 per cent stake in the company, now at over 26 per cent.
The Indian steelmaker, which bought the Mozambique project with Australia-listed Riversdale Mining, sees the mine as essential in ensuring it has a sustainable supply of coking coal.