20 Key Terms in the Mining Industry

The coal mining industry is one of Indonesia's strategic sectors. Based on data from the Directorate General of Mineral and Coal (Minerba) of the Ministry of Energy and Mineral Resources, there were 959 active mining companies in Indonesia as of the end of September 2025. In 2023, this industry also employed over 300 thousand workers, and this number is expected to continue growing in line with the development of energy and mineral projects across the country.

Given the significant job opportunities in this sector, understanding the basic mining terms is essential, both for prospective workers, students, and professionals who want to deepen their knowledge of the coal industry. To assist you, here are 20 key coal mining terms compiled alphabetically for easy learning.

1. Acid Mine Drainage (AMD): Acid mine water formed from the reaction of sulfide minerals with air and water. AMD requires proper management to prevent environmental pollution.

2. Backfill: The process of refilling the mined-out area using residual material as part of land reclamation.

3. Bedrock: The layer of hard rock beneath the overburden that forms the natural foundation of the mine.

4. Bench: A working step or level in an open-pit mine that serves as a path for heavy equipment.

5. Coal Expose: Coal that begins to be visible after the overburden layer has been removed.

6. Cycle Time: The duration of one work cycle for heavy equipment, such as loading, hauling, and returning to the loading point.

7. Fleet: A collection of heavy equipment used in mining activities, including excavators, shovels, and dump trucks.

8. Free Face: An unhindered face or surface of the mine that is easier for heavy equipment to dig.

9. Grade: The percentage or quality of valuable minerals contained in the mined material, including coal quality.

10. High Wall: A vertical or near-vertical wall formed by the excavation process in an open-pit mine.

11. Interburden (IB): Material or a layer of earth situated between two coal seams.

12. Idle: A condition when mining equipment is not being used or has no work assigned.

13. Open-Pit Mining: An open-surface mining method by excavating the earth's surface to form a large pit.

14. Overburden (OB): The layer of soil and rock that must be removed to access the coal seam.

15. Pit: A large hole in an open-pit mine that is the main location for coal excavation.

16. ROM (Run of Mine): Raw coal material taken directly from the pit before further processing.

17. Rip Rap: Large rock material used to control erosion and strengthen slope structures.

18. Road Maintenance: Maintenance of mine roads to keep them safe and suitable for the heavy equipment fleet.

19. Slope: The degree of inclination of a mine's slope that must be maintained to prevent landslides.

20. Smelting: The process of purifying minerals through melting to obtain pure metal.

By understanding these 20 basic terms, you will be better prepared to enter the complex and dynamic world of coal mining. This knowledge not only helps in understanding work processes in the field but also enhances the competency of anyone looking to grow in the energy and mineral resources industry.

By: Rizka S. Aji, Marketing Communication Specialist, PT.Sumberdaya Sewatama