The coal deposits are part of Tertiary coal bearing sediments preserved in the Cesar Rancheria basin. The basin is limited tectonically by the Oca Fault in the north and the Bucaramanga-Santa Marta Fault in the south and west. Two other structural features control the basin limits, an igneous and metamorphic complex to the northwest (Sierra Nevada de Santamarta) and the Perija Hills to the east which comprises Jurassic and Cretaceous sediments. These hills are an extension of the eastern Andean Mountains of Colombia (Cordillera Oriental).

The basin is subdivided into the Rancheria Basin in the north where the Cerrejon Mine is located and the Cesar Basin in the south with the Calenturitas and La Jagua deposits. Continuity of the coal measures between the two sub-basins has not been demonstrated.

The Calenturitas deposit is part of a regional synclinal structure (La Loma Syncline) and subsequent NE trending thrust faulting has resulted in the current distribution of numerous coal deposits in that area. The tectonic setting is predominantly compressive with NE-trending thrust faults the main structural features.

The La Jagua coal deposit is a synclinal basin formation approximately 5 km long and 2 km wide. The deposit is multi seamed and steeply dipping on both the north-west and south-east flanks. The centre of the deposit is much flatter with dips up to 5°. On the basis of borehole and mining records to date, faulting is not common and no major structures have been identified.

Both deposits are characterised with multiple dipping seams of variable thickness and quality.

The mining method is open cut mining. This is based on multi-seam, steep dip, truck and shovel open cut coal mining initially in strips to ex-pit dumps with a prog ession over time to haulback waste dumping in-pit. Small scale underground mining was undertaken at La Jagua but is no longer operating. Trials of highwall entry methods, such as auger mining, have been conducted at Calenturitas. The auger mining trial has been successfully completed and approximately 200kt of coal has been produced. This exercise has shown good roof stability in the auger holes, confirmed seam consistency and manageable methane gas levels were encountered giving early confidence for future plans to extract additional coal not included in this valuation.

MMC/MBGS observed that all ROM coal is crushed at each mine and is the loaded into trucks or trains without further processing. Coal is sold “unwashed”, meaning there is no metallurgical treatment required to achieve a saleable product. The yield is therefore 100%.