thumb|250px|a three-dimensional model of an underground mine with shaft access underground hard rock mining refers to various underground mining techniques used to excavate hard minerals, mainly those containing metals such as ore containing gold, silver, iron, copper, zinc, nickel, tin and lead, but also involves using the same techniques for excavating ores of gems such as diamonds. in contrast soft rock mining refers to excavation of softer minerals such as salt, coal, or oil sands. ==mine access== ===underground access=== accessing underground ore can be achieved via a decline (ramp), inclined vertical shaft or adit.  *declines can be a spiral tunnel which circles either the flank of the deposit or circles around the deposit. the decline begins with a box cut, which is the portal to the surface. depending on the amount of overburden and quality of bedrock, a galvanized steel culvert may be required for safety purposes. they may also be started into the wall of an open cut mine. *shafts are vertical excavations sunk adjacent to an ore body. shafts are sunk for ore bodies where haulage to surface via truck is not economical. shaft haulage is more economical than truck haulage at depth, and a mine may have both a decline and a ramp. *adits are horizontal excavations into the side of a hill or mountain. they are used for horizontal or near-horizontal ore bodies where there is no need for a ramp or shaft. declines are often started from the side of the high wall of an open cut mine when the ore body is of a payable grade sufficient to support an underground mining operation but the strip ratio has become too great to support open cast extraction methods. they are also often built and maintained as an emergency safety access from the underground workings and a means of moving large equipment to the workings. ===ore access=== levels are excavated horizontally off the decline or shaft to access the ore body. stopes are then excavated perpendicular (or near perpendicular) to the level into the ore. ==development mining vs. production mining== there are two principal phases of underground mining: development mining and production mining. development mining is composed of excavation almost entirely in (non-valuable) waste rock in order to gain access to the orebody. there are six steps in development mining: remove previously blast
Underground_mining