Indium · element 49
The soft, silvery metal you touch every day without knowing it, hidden inside every touchscreen
Key facts
Indium is one of the metals that make modern screens possible. Every smartphone, tablet and flat-panel television carries a layer of indium tin oxide so thin it is invisible. It conducts electricity yet lets light through, a rare combination that lets your finger talk to the glass.
The metal itself is unusual too. It is soft enough to dent with a fingernail, melts at a temperature you could reach in a kitchen, and sticks to glass in a way most metals do not. It is one of the rarer elements in the crust, and almost all of it is recovered as a by-product of zinc mining.
Where it is found
Indium never forms deposits worth mining on their own. It is scattered through the Earth's crust at roughly a quarter of a part per million, similar in abundance to silver, but it does not concentrate into rich veins. Instead small amounts substitute for zinc in the mineral sphalerite and for other metals in some tin and copper ores.
When zinc concentrates are roasted and leached, the indium ends up in residues and flue dusts, and refiners with the right equipment extract it from there. China produces the largest share, with South Korea, Japan and Canada also important. Because supply depends on zinc output rather than on demand for indium, prices have been volatile, and recycling the material sprayed onto screens during manufacturing has become an important secondary source.
How it was discovered
Indium was found in 1863 by two chemists at the Freiberg mining academy in Saxony, Ferdinand Reich and Hieronymous Theodor Richter. Reich was searching zinc ores for the recently discovered element thallium, and he produced a yellow precipitate that did not behave like any known metal. He wanted to check its spectrum, but Reich was colour-blind, so he asked Richter to look.
Richter saw a brilliant line in the indigo-blue part of the spectrum that matched nothing recorded, and the pair named the new element indium after that colour. They isolated a small amount of the metal soon after and displayed it at the Paris World Fair of 1867. The two men later fell out over who deserved the credit.
What we use it for
Indium tin oxide accounts for most of the indium used. It is deposited as a coating a few hundred nanometres thick onto glass or plastic. Being transparent and conductive, it forms the electrodes in liquid crystal displays, touchscreens, some solar cells, and the heated windscreens of aircraft.
Indium also appears in semiconductors. Indium phosphide and indium gallium arsenide are used in lasers and detectors for fibre-optic communications, and indium gallium nitride is part of the blue and white LEDs that light modern homes. Because indium is soft and melts at a low temperature, it is used in solders, in seals that must stay leak-tight at very low temperatures, and in thermal pastes that carry heat away from computer chips.
Reading the numbers
Indium melts at 156.6 °C, lower than the temperature of a hot oven, and boils at about 2072 °C. Its density is 7.31 grams per cubic centimetre, slightly less than iron and around seven times that of water.
The configuration [Kr] 4d10 5s2 5p1 places indium in group 13, under aluminium and gallium and above thallium. With three outer electrons, indium most often forms compounds in the +3 state, though a +1 state also exists and becomes more common further down the group. Its first ionisation energy of 558 kilojoules per mole is fairly low, and its electronegativity of 1.78 is modest, consistent with a reactive but not violently reactive metal. Indium sits in the p block, so it is a post-transition metal: it has the softness and low melting point that go with a full d shell tucked away beneath the bonding electrons.
Safety and the environment
Indium metal is considered low in toxicity when handled as a solid, and it has been used in dental alloys and in some medical imaging agents. The concern is with fine particles. Workers who breathe indium tin oxide dust have developed a specific lung disease, first identified in Japanese display factories in the early 2000s, and workplaces now control exposure carefully.
Environmentally, indium is too rare to be a widespread pollutant, but the mining and smelting of zinc that produces it has its own footprint. Recovering indium from scrap screens is technically difficult because the layers are so thin, and improving this recycling is an active area of research.
Did you know?
- Indium is soft enough to be scratched with a fingernail and, like tin, gives a faint crackling sound when bent as its crystals shift.
- Ferdinand Reich, who first isolated indium compounds, was colour-blind and had to ask a colleague to identify the element's indigo spectral line.
- A drop of molten indium wets clean glass and sticks to it, which makes it useful for sealing glass to metal in scientific instruments.
- An alloy of gallium, indium and tin, called galinstan, is liquid at room temperature and is used in some thermometers in place of mercury.
- The whole world uses well under two thousand tonnes of indium a year, a tiny quantity compared with the millions of tonnes of zinc it is extracted from.
More in the post-transition metals
Column-mates come first, since elements in one column have outer electrons arranged in a similar way and tend to behave alike; the rest are the nearest neighbours in the family.
See all 12 post-transition metals on one page, or browse all 118 elements.
Frequently asked questions
What is indium used for in phones?
Phone screens have a transparent conductive coating of indium tin oxide. It carries the electrical signals that detect your finger on a touchscreen and drives the pixels in the display, while letting light pass through almost unhindered. No other material has matched this combination at large scale.
Is indium rare?
It is scarce but not among the rarest elements. Indium is about as abundant in the crust as silver, but unlike silver it never concentrates into rich ores, so it is recovered only as a by-product of zinc refining. Total world production is under two thousand tonnes a year.
Is indium toxic?
Solid indium metal is low in toxicity and can be handled safely. The main risk is breathing fine indium tin oxide dust in factories, which has caused a serious lung disease in some workers. Ordinary users of screens and electronics are not exposed to it.
Why is indium called indium?
It is named after the colour indigo, not after India. When Reich and Richter examined their new element in 1863, its spectrum showed a bright line in the indigo-blue region that no known element produced, and they named it after that line.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Indium reference article. Spotted an error? Tell us.