Chromite Mining Process

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What is Chromite?Chromite ore is rock that contains a high enough concentration of chromite to have economic value. Chromite is the principle ore of the element chromium. Chromite is a key industrial mineral used for manufacturing stainless steel because of its very high melting point.

Rock Containing Chromite Ore

Extraction of the Chromite OreBoth surface and underground mining methods will be used to mine the chromite. Mining produces both ore and waste rock. Waste rock consists of all other non-chromite bearing rock excavated during mining.

Surface MiningChromite ore is mined first by surface methods. This includes an open pit from which surface material, non-chromite bearing overburden and chromite ore, will be excavated. The chromite ore containing rock will be drilled, blasted, removed and loaded onto large trucks for hauling to the crusher and ore processing facility.

Underground MiningThe transition to underground mining will be considered once it is necessary to extract rock from greater depths. The underground mine will be reached from the bottom of the open pit. Blasthole stoping methods will be used for underground mining. Stoping occurs in underground mineral mining when the surrounding rock is strong enough to allow the drilling, blasting, and removal of ore without caving.

How Does Blasthole Stoping Work?1. The ore is drilled and blasted. The blasted ore is

then removed from a lower-level entry point called a draw point.

2. The resulting open section or stope is then filled-in before moving onto the next section.

3. Each stope will be developed by creating horizontal tunnels or drifts in the rock parallel to the ore body.

4. Large loaders or scoop trams will move the ore to trucks for transportation to the surface.

Surface Mining

Blasthole Stoping

Pit Bench

Access RoadAccess Road

Pit Bottom

Long-hole drilling and

blasting

Stope

Blasted oreUndercut

Draw point Loading crosscut

Transport drift

Chromite Mining Process

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Processing Chromite Ore extracted from the mine with a grade of 40% chromium oxide or greater is suitable for processing directly in the off-site ferrochrome production facility. Ore with a lower grade must be processed to increase its chromite content. Ore that is not suitable to ship directly to the ferrochrome production facility will be processed at the mine site to produce concentrate.

The processing of chromite ore separates and concentrates the valuable chromite mineral. This involves mechanical processes and separation using gravity. The result is a concentrate suitable for refining, and tailings that have no economic value. Tailings are the materials left over from the ore processing facility after the chromite has been extracted from the ore. Tailings will be managed over the long-term at the mine site in a tailings management area.

Development of Ferrochrome The final product of the ore and concentrate will be ferrochrome. Ferrochrome production occurs in enclosed electric arc furnaces at a temperature of approximately 1,700 oC. This will produce a melted ferrochrome metal product called matte. Matte is then moulded and compressed into a marketable product.

Ferrochrome

The Mining Process

Definitions

Ore: a mixture of minerals from which at least one of the metals (e.g., chromite) can be extracted at a profit

Waste Rock: consists of other non-chromite ore excavated during mining

Tailings: non-chromite rock produced from ore processing

Concentrate: a fine, powdery product of processing containing a high percentage of valuable metal