sentences:  At particularly deep depths, room and pillar mining can be more cost effective compared to strip mining due to the fact that significantly less overburden needs to be removed.This means that today, room and pillar mining is mostly used for high grade, but small, deep deposits.Due to a recovery rate as low as 40% in some cases, room and pillar mining cannot compete in terms of profitability with many modern, more mechanized types of mining such as longwall or surface mining.