Hard rock mining: Encyclopedia II - Hard rock mining - Ore extraction

Hard rock mining - Ore extraction

There are a number of mining methods that are used to extract the mineral bearing rock (ore) from the uneconomic rock, also known as mullock or gangue. Typically some means of support is required in order to maintain the openings that are made by mining. This can be done by pillars which are then mined following the backfilling of the initial stopes. Local to the ore drive, rock bolts, mesh and shotcrete are used to secure working faces and the backs (tops) of the drives.
However, leaving pillars of ore is wasteful, as that ore cannot be extracted and processed.

Hard rock mining - Stope and retreat

Using this method, mining is planned to extract rock from the stopes, and allow the wall rocks to cave in to the extracted stope after all the ore has been removed. Then, the drive is sealed.

Hard rock mining - Stope and fill

Where large bulk ore bodies are to be mined at great depth, or where leaving pillars of ore is wasteful, the open stope can be filled with a cement and waste rock mixture, which solidifies and forms a solid fill. This method is especially popular, as the refilled stopes provide support for the adjacent stopes, allowing total extraction of economic resources.

Adapted from the Wikipedia article "Ore extraction", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki