Hard rock mining
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Hard rock mining refers to various techniques used to mine ore bodies by creating underground "rooms" or stopes supported by surrounding pillars of standing rock. Terms for this include
- stope and pillar
- room and pillar
- longhole stoping
- benching
- vertical crater retreat
- block caving
- sub level caving
Hard rock mining is used for mining many ore types such as gold, copper, zinc and diamonds.
There are a number of mining methods that are used to extract the mineral bearing rock from the host rock. Typically some means of support is required in order to maintain that openings that are made by mining. This can be done by pillars which are then mined following the backfilling of the initial stopes.
Coarse ore is mucked out using gravity to help move it down rock raises or shafts to waiting trains of ore cars used to move it to the surface These trains can travel through long drifts or tunnels ending in portals to the mills on the surface. Ore is also moved in skip buckets hauled up shafts and emptied into bins beneath surface headframe towers for transport to the mill. Ore is also hauled in large trucks up declines to the surface.
Open pit mining is used in shallow orebodies, often at much lower grades of mineralisation.
Trivia
The deepest hard rock mine in North America is a nickel mine in Sudbury, Ontario. The deepest hard rock mines in Australia are the copper and zinc lead mines in Mount Isa, Queensland.