Pre-Tertiary, Eocene and Oligocene sedimentary rocks are present in the Tanjung Redeb area but none are found in the Berau Coalfield (Lati, Kelai and Binungan areas). The Eocene and Oligocene sediments are dominantly marine, fine grained clastic rocks with rare volcanic units, although non-marine sandstones and minor coal deposits occur immediately above the basal Tertiary unconformity.

The oldest rocks present in the Berau Coalfield are of Miocene age and belong to the Sterile Formation. This formation is composed of marine mudstone, siltstone and sandstone. The sandstone is massive and fine- to very fine-grained and it is interbedded with mudstone and siltstone. Burrows are common in all lithologies.

The Sterile Formation conformably underlies the coal-bearing Berau Formation although the contact between the formations is difficult to place in the Berau Coalfield. The Berau Formation, at least 400 metres thick, contains interbedded mudstone, siltstone, sandstone and coal. Shell fossils, plant impressions, coal flakes and burrows are common, particularly in the mudstone.

The coal measures of the Tarakan Basin occur in the Berau Formation which contains at least 19 seams. The thicknesses of the seams range from a few centimetres up to 4.5 m with dips of 5° to 20°. Exposure of the seams is good and they can be traced in three geographic areas which correspond to structural zones formed by post Miocene folding - Kelai, Lati and Binungan.

PT Berau Coal, the main operating subsidiary of the Company, owns a 118,400 ha mining concession area located in the Berau Regency, approximately 300 kilometers north of Samarinda, the capital city of the East Kalimantan province. The concession area is based on a letter from the Ministry of Energy and Mineral Resources No. 178.K/40.00/DJG/205 dated 7 April 2005 and valid until 2025, with possible extension options, 2 x 10 years.

PT Berau Coal has three principal open cut mining operations; Lati, Binungan, and Sambarata, located in an 118,400 hectare concession area.

Mining is similar to that of Lati and Binungan. The coal is extracted using hydraulic excavators and loaded into dump trucks.

From the mine coal is transported to the coal processing plant a distance of some 2.0 kilometres. The coal is crushed blended and placed onto stockpiles. It is theen loaded into barges.