The various grades of coal suitable for carbonization to make coke for steel manufacture. Methane A potentially explosive gas formed naturally from the decay of vegetative matter, similar to that which formed coal. Methane, which is the principal component of natural gas, is frequently encountered in underground coal mining operations and is kept within safe limits through the use of extensive mine ventilation systems. Opencast mine, suface mining A form of mining in which overburden is removed to expose the coal seams and allow their extraction by surface means. Overburden Layers of soil and rock covering a coal seam.
Overburden is removed prior to surface mining and replaced after the coal is taken from the seam.
A physical, or non-chemical, test of coal. Not precise, but very useful for determining the commercial value. Sulfur and Btu content are also generally reported with a proximate analysis. The classification of coal by degree of hardness, moisture and heat content. It is the most common coal and is used to generate electricity and to make coke for the steel industry.