The merger with Whitehaven received shareholder approval in April, later followed by court approval on April 18.

Following approval, Whitehaven has acquired unlisted exploration and development company Boardwalk Resources, which owns four coal exploration assets across New South Wales and Queensland.

The merger of the three companies will create a coal company with saleable production of 6 million tonnes per annum of coal in the 2012 financial year.

Under the scheme of arrangement, Aston shareholders will receive 1.89 Whitehaven shares for each Aston share they hold.

Implementation of the scheme is expected on May 2.

In addition to the merger, Aston received Planning Assessment Commission approval for its flagship Maules Creek project in the Gunnedah Basin of New South Wales, subject to the implementation of appropriate regional management frameworks and mine-specific management plans and conditions.

Maules Creek is tipped to produce 10Mtpa of coal, with first coal predicted for 2014.

In October last year, Aston entered into an agreement with Japanese company J-Power Australia to offload a 10% stake in Maules Creek for $A370 million.

As part of the agreement, J-Power Australia will also gain a 10-year thermal coal sales contract with Aston.

Last month, trading house Itochu approved the transaction.

Aston said it was continuing to work through the outstanding conditions precedent and expected to complete the transaction in the second quarter of 2012.