The Senakin mine, South Kalimantan, operated by PT Arutmin Indonesia mines Eocene age coal. This economically important coal occurs near the base of the T2 member of the Tanjung Formation The laterally continuous basal coal unit is up to 9 m thick, but is more typically 4 to 6 m.

The lower part of the Eocene seam is low in sulfur, whereas the upper part has higher levels due to increased pyrite content or subsequent sulfate alteration. The coal bed varies vertically in ash and sulfur content but this variation is laterally consistent and predictable.

Arutmin operates 6 open cut coal mines: Senakin, Satui, Mulia, Batulicin, Asam-asam and Kintap, all strategically located near Arutmin’s port facility – North Pulau Laut Coal Terminal (NPLCT) in the north shore of Pulau Laut.