How chromite is mined

Chromite forms flat black layers deep in cooled magma, some hundreds of kilometers long and only meters thick.

stations: 4
things downstream: 48

The short version

Chromite settles out of slow-cooling magma into thin dark layers, and miners reach them from underground or the surface. Rich lumpy ore can go straight to a furnace. The rest is crushed, screened and slurried, then run down spiral chutes where the heavy chromite hugs the inside of the curve. Cleaning passes lift it to about 42%, a grade ferrochrome smelters can use.

Follow the dark layer

Most reserves lie in stratiform deposits, thin even layers spread over a broad area, and pod-shaped deposits matter too. Both underground and surface methods are used. Rich lump ore above 46% chromic oxide can go directly to ferrochromium production.
Crush and screen

Ore is crushed and screened into size fractions. The fine fraction, typically 1.0 mm or less, is mixed with water to a set density and deslimed to remove ultrafine particles.
Run the spirals

Slurry is pumped to the top of a spiral and flows around it. Fast-settling heavy grains drift to the inside of the channel, while light waste rides the faster water on the outside and heads to tailings.
Clean to smelter grade

The chromite stream passes through cleaning and recleaning spirals that remove misplaced waste. Grade climbs to typically 42%, ready for ferrochrome smelters, and spirals can also make chemical and foundry grades.

typically 42%

End of the lineChromite Next it goes into chromium.

Worth repeating

Chromite forms inside slow-cooling magma and also occurs in iron meteorites.
The Bushveld in South Africa is one of the great chromite-bearing intrusions.
Tailings thrown out by platinum concentrators in the Bushveld are rich enough in chromite to be run through spirals again.