What would be a good use for the unwanted rock material from the crushed ore?

Question

In mining, what could they do with the unwanted rock material after they crush the ore.

Answer 1

Inferior sources of iron ore generally required beneficiation. Due to the high density of hematite relative to silicates, beneficiation usually involves a combination of crushing and milling as well as heavy liquid separation. This is achieved by passing the finely crushed ore over a bath of solution containing bentonite or other agent which increases the density of the solution. When the density of the solution is properly calibrated, the hematite will sink and the silicate mineral fragments will float and can be removed.

Taconite mining involves moving tremendous amounts of ore and waste. The waste comes in two forms, bedrock in the mine (mullock) that isn't ore, and unwanted minerals which are an intrinsic part of the ore rock itself (gangue). The mullock is mined and piled in waste dumps, and the gangue is separated during the beneficiation process and is removed as tailings. Taconite tailings are mostly the mineral quartz, which is chemically inert. This material is stored in large, regulated water settling ponds.

Magnetite is beneficiated by crushing and then separating the magnetite from the gangue minerals with a magnet. This is usually so efficient that lower grade ore can be treated when it is magnetite than a comparable grade of hematite ore, especially when the magnetite is quite coarse.

To convert an oxide of iron to metallic iron it must be smelted or sent through a direct reduction process.