What is NOT a characteristic of 'High coal' in a mining operation?

The correct choice indicates that "High coal" is defined by its height, specifically referring to coal seams that are greater than 48 inches in thickness. In mining operations, this terminology is crucial because it directly affects the mining methods used and the potential production rates.

When coal seams are classified as "High coal," they typically offer advantages in terms of extraction efficiency and yield, making them desirable for mining. Additionally, the characteristics of "High coal" imply that it is substantial enough to contribute effectively to supporting the roof of the mine, enhancing stability during operations. Accessibility from a portal also suggests that the coal seam can be efficiently mined and transported.

Thus, being less than 48 inches does not fall under the definition of "High coal," which centers on the aspect of coal seam height, reinforcing that greater dimensions are essential to classify the coal as "High."