What type of coal deposits are accessed with subsurface mining techniques?

Subsurface mining is a method used to extract minerals and ores that are located deep underground. This is different from surface mining, where minerals are extracted from the surface or shallow depths. In subsurface mining, tunnels or shafts are dug into the ground to reach the deposits, and various techniques are used to remove the material. This method is often used when surface mining is not feasible due to the depth of the deposit or environmental concerns.

There are four main types of coal deposits, which are classified based on their age and the amount of heat and pressure they have been subjected to. These are: 1. Peat: The youngest type of coal, formed from decaying plant material. It has the lowest carbon content and is not used for commercial purposes. 2. Lignite: A soft, brownish-black coal formed after peat. It has a low energy content and is used mainly in power plants for electricity generation. 3. Bituminous coal: A harder, black coal with a higher energy content. It is used in power plants as well as in the production of coke, which is used in steelmaking. 4. Anthracite: The oldest and hardest type of coal, with the highest carbon content and energy content. It is used for space heating and industrial processes that require high temperatures.

Subsurface mining techniques are typically used for coal deposits that are located deep underground, as the risk, cost, and environmental impact of surface mining become unfeasible. With this in mind, the type of coal deposits accessed with subsurface mining techniques are generally the deeper and more valuable deposits: bituminous coal and anthracite. Both of these types of coal have higher energy content compared to lignite and peat, making it more economically viable to use subsurface mining methods to access them.