Chromium is a metal highly resistant to corrosion and heat, making it an industrial commodity used extensively in high-strength alloys. Approximately half of all chromite production goes into the manufacture of stainless steel, where chromium imparts its unique properties to the alloy. The metal is obtained solely from its ore, chromite (\(\text{FeCr}_2\text{O}_4\)).
The Source Material: Understanding Chromite
Chromite is an oxide mineral belonging to the spinel group. While many minerals contain trace amounts of chromium, chromite is the only one found in deposits large enough to be economically mined. In its natural state, the ore is a brownish-black mineral that occurs in basic and ultrabasic igneous rocks. The formation of these deposits begins as cooling magma crystallizes, resulting in two primary types: stratiform and podiform. Stratiform deposits are large, layered intrusions hosting massive, continuous seams of the ore, while podiform deposits are smaller, irregular bodies found in metamorphic rocks like serpentinite.
Global Hotspots of Chromium Production
The geographical distribution of chromite reserves is highly concentrated, with the vast majority located in just a few nations. South Africa is the world’s leading producer and holds the largest global resources and reserves of chromium ore, accounting for 39% of global chromite output in 2021 (around 18 million metric tons). This dominance stems from the Bushveld Igneous Complex, a massive geological structure containing a significant portion of the world’s known chromite reserves. The ore from this complex often yields an average of 44% \(\text{Cr}_2\text{O}_3\), which is substantially higher than the global average. The country’s mines, mostly located in the Mpumalanga and Northwest Provinces, tap into these rich, layered stratiform deposits.
The next largest producers are Kazakhstan and Turkey, which each produced approximately 7 million metric tons of chromite in 2021. Kazakhstan boasts the world’s largest chromium ore reserves, estimated at around 230,000 tonnes, with its deposits often featuring exceptional grades of up to 52% \(\text{Cr}_2\text{O}_3\). India is also a significant player, ranking fourth globally with production figures around 3 to 4.2 million metric tons in recent years.
Extraction and Initial Processing
Chromite ore is extracted from the ground using both open-pit and underground mining techniques. Open-pit mining is employed when the orebody is near the surface, while the deeper, layered stratiform deposits, like those in the Bushveld Complex, require extensive underground mining operations. The goal of the initial extraction phase is to physically remove the chromite-bearing rock from the surrounding waste material, known as gangue.
Once the ore is brought to the surface, it undergoes a multi-stage process of crushing and grinding to reduce the rock to smaller particle sizes. This liberation of the chromite mineral from the gangue is necessary before the concentration stage can begin. The primary method used for concentration is gravity separation, which exploits the high density of chromite compared to the lighter waste rock. Gravity separation techniques, such as using shaking tables or spiral concentrators, are highly effective in separating the heavier chromite particles. The resulting chromite concentrate is then ready for further processing, typically to produce ferrochrome, the iron-chromium alloy used in stainless steel production.