The sale is expected to be completed by the middle of next month, subject to regulatory approvals.
Located 180km west of Mackay, North Goonyella produces high-quality hard coking coal for export from Hay Point to steel mills in Japan, other parts of Asia, and Europe.
The underground mine, which began longwall production in early 1994, produced 2.4 million tonnes in the year to June 30, 2000.
RAG will manage the project and take responsibility for coal sales, while Thiess will be the operator under contract to the project.
The two companies own and operate the nearby Burton open pit coal mine and expect to be able to achieve synergies through coordinated management of both projects.
Sumitomo Corp will continue to assist the new consortium with marketing of North Goonyella coal in Japan.
