Coal is formed by the way of a real complex and requires old time (tens of until hundreds of million years) under physics influence, chemical and situation of geology. To comprehend how coal formed from flora it is important to know where coal formed from flora it is important to know where coal formed and factors which will influence it is and form of coal seam.

There is 2 kinds of theory expressing place the forming of coal, that is :

A. The Insitu theory

This theory express that coal seam former material the forming of place of where the origin flora stays. Thereby after the plant is death, has not experienced transportation process, soon piled up by sediment layer and experiences process coalification. Coal type formed in this way has wide spreading and flattens, the quality is better because its(the ash content is small relative, Can be met at coal field Muara Enim (South Sumatera).

B. The Drift theory

This theory express that coal seam former material the forming of place differing from place of the origin flora stays. Thereby after the plant is death, transported by water media and accumulates a place, soon piled up by sediment layer and experiences process coalification. Coal type formed in this way has spreading is not wide but met some place, the quality is unfavourable because many containing pollutant material transported together during process transportation of from crop provenance to place of sedimentation. Can be met at delta coal field Mahakam Purba, Easth Kalimantan.