Limestone is surface mined through open pit quarries or hillside cuts, or horizontally by tunneling under the overlaying surface rock. Quarrying is the most common method used, because it is an easier and cheaper method for removing shallow deposits. Underground operations are used when the overlaying surface rock is too thick.
Quarry operations remove the surface material covering the limestone deposit, drill holes for explosive material and blast the underlying material free. The particulate material recovered is hauled away for processing. If the material from the blast is too large to remove from the quarry, a rock crusher is employed to reduce it to rubble small enough for transport. Factors that determine whether surface mining is suitable include the size and shape of the deposit, haul distances, location relative to urban centers, and environmental concerns and regulations.
Underground mining is used in areas where the environmental impact of a surface operation is too great or the limestone deposit is located too deep. Most underground mining uses the room-and-pillar method, in which the limestone is removed by blasting, and columns of the rock are left to support the roof. These mines can be very large, with roof heights up to 30 meters and extending for many acres.