How indium is recovered

Indium is about as scarce as silver, and all of it is a by-product of refining other metals, chiefly zinc.

stations: 5
things upstream: 5
raw sources: 4
steps from the ground: 2

The short version

Indium forms no mineable deposits of its own. It is recovered from sulfidic zinc ores, where it rides along in the mineral sphalerite. During the roast-leach-electrowinning route for zinc, indium builds up in the iron-rich residues, and refiners then extract it. LCD screens use about half of it.

Roast the zinc concentrate

Zinc ore concentrate is roasted. Indium travels with the zinc through the early steps.

Goes in
Zinc ore
Leach with acid

The roasted material is dissolved in acid so the zinc can be recovered by electrowinning. Not everything dissolves.

Goes in
Sulfuric acid
Collect it in the residue

Indium accumulates in the iron-rich residues left from zinc leaching. These residues are the feedstock for indium refiners.
Refine to metal

Indium is separated from the residue and refined to a soft, silvery metal. Output is limited by how much zinc ore is mined each year.
Cast into ingots

The refined metal is melted and cast into ingots for sale to display makers.

End of the lineIndium Next it goes into led, indium tin oxide.

Worth repeating

Indium sits at about 50 parts per billion in Earth's crust, a similar abundance to silver.
LCD screens account for about half of indium consumption.
The first large-scale use of indium was coating bearings in World War II aircraft engines.