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Material World
Element · In

Indium

A soft metal nobody would notice, except that every touchscreen depends on it.

Electrical conductor

Indium tin oxide is transparent and conducts electricity, a combination almost nothing else manages at useful quality. Every liquid-crystal display and capacitive touchscreen has a layer of it, which is why a metal produced in tonnes rather than thousands of tonnes sits inside a billion devices.

It is recovered almost entirely as a by-product of zinc refining, so indium supply is set by zinc demand rather than by anything to do with displays. Substitutes have been sought for two decades with limited success.

Uses

Indium's dominant use is indium tin oxide, the transparent conductor coating almost every flat panel display and touchscreen. A material that conducts electricity while remaining transparent is rare, and no substitute has displaced it at scale.

Indium is also very soft and stays ductile at cryogenic temperatures, which makes it a gasket and seal material for vacuum and low-temperature equipment. Indium solders join surfaces that ordinary solder will not wet, and indium compounds appear in LEDs and thin-film solar cells.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is sourced from

  • Zinc — element · recovered almost entirely from zinc refining, so indium supply is set by zinc demand

is used as

  • Lighting — application · as the transparent electrode in displays
  • Photovoltaics — application · in thin-film cells, alongside its larger use as the transparent electrode

is extracted from

  • Sphalerite — mineral · a by-product of zinc refining, which is why indium supply follows zinc demand rather than its own

is found in

  • Indium tin oxide — material · the bulk of it, and where most of the world's indium goes Wikidata

is produced by

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
  • PubChem
    US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors
  • NIST — National Institute of Standards and Technology
    United States Department of Commerce · US Government work — public information, credit requested

Questions this page answers

Where it comes from, and what it becomes

Follow Indium back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Indium → is sourced from (recovered almost entirely from zinc refining, so indium supply is set by zinc demand) → Zinc → is produced by (as the oxide, which is then reduced — roasting is the step that makes zinc sulfide smeltable) → Roasting → takes as input (a copper sulfide; roasting drives off the sulfur that would otherwise prevent reduction) → Chalcopyrite
  • Indium → is produced by (from the residues of zinc refining, which is the only source there is; indium ore does not exist in any workable sense) → Solvent extraction and electrowinning → takes as input (in the low-grade and oxidised ores that flotation cannot economically treat, with bacteria oxidising the sulfide into a form the acid can attack) → Chalcopyrite
  • Indium → is extracted from (a by-product of zinc refining, which is why indium supply follows zinc demand rather than its own) → Sphalerite
  • Indium → is produced by (from the residues of zinc refining, which is the only source there is; indium ore does not exist in any workable sense) → Solvent extraction and electrowinning → takes as input (a carbonate dissolves straight into acid, which is why an oxidised orebody goes to a leach pad and the sulfide beneath it goes to a smelter) → Malachite
  • Indium → is produced by (from the residues of zinc refining, which is the only source there is; indium ore does not exist in any workable sense) → Solvent extraction and electrowinning → takes as input (leached with acid or alkali depending on the host rock, which is what decides the flowsheet of a uranium mill) → Uraninite
  • Indium → is sourced from (recovered almost entirely from zinc refining, so indium supply is set by zinc demand) → Zinc → is produced by (as the oxide, which is then reduced — roasting is the step that makes zinc sulfide smeltable) → Roasting → takes as input (roasted for its sulfur as much as for its iron) → Pyrite

These are the most distinct paths back. Indium can be traced through others besides.

Downstream — what it becomes

  • Indium → is used as (as the transparent electrode in displays) → Lighting
  • Indium → is used as (in thin-film cells, alongside its larger use as the transparent electrode) → Photovoltaics