Systematic mining activities have been carried out for the past four centuries. The scale of these activities was always on the increase. In the initial period ore reserves were near the surface of the earth and could be easily accessed, directly i.e. without a need for removal of a significant quantity of overburden. In those days the final materials such as coal, or minerals of gold, iron, copper etc. were produced at low cost. With the passage of time the demand for such final materials increased. ‘Easy to recover’ reserves dwindled and larger quantities of overburden were required to be removed to access the mineral of interest. It became essential to take advantage of mining machinery. As a result, the cost of minerals increased.