Speculation is mounting that Tinkler would sell out of Aston at the right price and make Boardwalk — which owns 19.9% of Coalworks — his principle mining focus.

Another theory is that Tinkler used Boardwalk’s stake in Coalworks to engineer a board reshuffle in that company last week. Some market analysts are tipping that he wants to increase his shareholding in Coalworks to make it more attractive for the IPO, which is being managed by Morgan Stanley.

Coalworks and Boardwalk are also joint venture partners in the Ferndale project in New South Wales.

Coalworks entered into a JV agreement with Boardwalk Ferndale Pty Ltd, a Nathan Tinkler–controlled company, which allows Boardwalk to acquire a 50% holding in EL7430 (Ferndale), by spending up to $25 million to fund a bankable feasibility study for an open cut mine and a pre–feasibility study for an underground mine.

At the end of the 2011 financial year, expenditure totalled $1.8 million and the JV, which is being managed by Boardwalk, expected production to begin in 2016.

“It appears we can successfully initially target an open cut mine and conceptual studies for underground and open cut is scheduled for the end of December 2011,” Coalworks chairman Wayne Mitchell told its recent annual general meeting.

Tinkler – who owns 31% of Aston – installed the chief executive of Boardwalk Peter Kane at the helm of Aston in place of current chief executive Todd Hannigan.

Prior to joining Boardwalk earlier this year, Kane was the chief operating officer for Macarthur Coal, where he was responsible for all operational aspects and project development.

Aston, which owns 85% of the Maules Creek mine in the Gunnedah Basin of NSW, is seen as an attractive asset for a global company looking for a piece of an emerging coal province.

Coalworks’ Vickery South project is also near Aston’s Maules Creek mine.

Tinkler made most of his fortune developing the Macarthur Coal company, which was eventually sold to Peabody Energy for $4.9 billion.