Hard Rock Mining
Hard rock mining is a type of underground mining. In this type of mining, a hole is made that is more commonly known as an adit. Tunnels are dug inside the ground and are either blasted with dynamite or drilled out; these tunnels more commonly known as shafts. Shafts are dug vertically downwards into the ground. Every shaft has a function. There will be one shaft for example that will be utilized by the miners as a way in and out of the mine; another shaft might be utilized to mine the machinery. A different shaft is utilized for air or ventilation. As soon as the miners reach the base of the shafts, there is an additional tunnel that guides to the rocks or minerals. Tunnels can be slanted or sloped. These mines are somewhat similar to an underground building. The tunnels in a hard rock mine are separated into rooms with rock pillars. As soon as the mine owners and the engineers decide that it is time to discontinue taking material from the mine, they carry out a process that is known as robbing the pillars and this basically means that as they back out of the tunnels, they remove the mineral out of the pillars that hold up the roof. When this is done the roof then caves in. This is process needs to be done with extreme caution. Hard rock mining is one of the most dangerous kinds of mining. To begin with, this type of mining is done underground. It can be very deep underground. Certain mines have lethal gases in them therefore miners have to always be prepared for cave-ins, explosions, and gases. Some of the minerals that can be found when doing hard rock mining are gold, copper, zinc, lead, and diamonds.
This is on average the lowest cost per ton underground mining technique that exists. It does have need of extensive upfront development costs as huge excavations need to be made to undermine the block that is to cave, and big milling infrastructure needs to be set up to hold the big ore tonnages that a profitable cave will bring about. Once the ore block has been undermined, the ore block is broken over time by gravity and the pieces fall down the finger raise. The dimension of the pieces that go through to the chutes for loading is controlled by strong sieves or grizzlies on the grizzly level.