The buyers of Solid Energy's main coal mines will pay $46 million up front, and could pay as much as $50m extra if coal prices rise.
Phoenix Coal - a partnership of coal company Bathhurst Resources and food group Talley's - is buying the Stockton mine on the West Coast, and the Rotowaro and Maramarua mines in Waikato, subject to regulatory approval.
Solid Energy was put into administration a year ago, when it couldn't pay back almost $400m of debt because of a slump in world coal prices and demand that battered its earnings.
In a release to the Australian Stock Exchange, Bathhurst said the joint venture would pay up to $50m, provided coal from the Stockton mine fetched at least $150 a tonne.
World coal prices have doubled in the past few months as China has closed down uneconomic mines and imported more.
But a global price benchmark still put the average price at about $104 a tonne.
The new Phoenix Coal has raised $55m, with Bathhurst investing $26m, Talley's $14m, and the BNZ providing $15m in debt. After paying for the mines the company will have $9m in working capital.
Several smaller former Solid Energy mines have been sold to private mining or investment companies.
The sale of Solid Energy assets was all but complete with creditors - mainly banks - likely to be repaid about half of what they are owed.