Antimony · element 51
An ancient eye cosmetic turned modern flame retardant, and the reason lead-acid batteries hold their shape
Key facts
Antimony sits on the staircase of metalloids that separates metals from non-metals. It looks like a metal, silvery and shiny, but it is brittle, conducts electricity poorly and behaves chemically like a cross between a metal and a non-metal. That in-between character has made it useful in surprising ways for thousands of years.
The ancient Egyptians ground its sulfide into black eye make-up. Medieval alchemists were fascinated by it. Today its main jobs are far less mystical: hardening the lead plates in car batteries and helping plastics resist fire. It is a small-volume element, but one that many industries would struggle to replace.
Where it is found
Antimony's chief ore is stibnite, a grey sulfide mineral that forms striking clusters of blade-like crystals. It is found in hydrothermal veins, often alongside other sulfides. Antimony also occurs in small amounts as the native element and in oxidised minerals formed where stibnite has weathered. It is rare in the crust overall, at well under a part per million.
China has long dominated production, with the Xikuangshan district in Hunan province historically the largest source in the world. Russia, Tajikistan, Bolivia and Myanmar also mine antimony. Because so much comes from one country, antimony appears on many national lists of critical raw materials whose supply is considered at risk.
How it was discovered
Antimony compounds were used long before anyone knew the element existed. The Egyptian cosmetic kohl was often powdered stibnite, and antimony objects several thousand years old have been found in Mesopotamia. The metal itself was probably produced occasionally by accident in ancient smelting.
The first clear written account of how to extract antimony metal appears in Vannoccio Biringuccio's De la Pirotechnia, printed in Italy in 1540. Alchemists in the following century wrote extensively about it, and a book called The Triumphal Chariot of Antimony, attributed to a monk named Basil Valentine, made the element famous. The symbol Sb comes from stibium, the Latin word for stibnite. The origin of the name antimony is uncertain, though it probably derives from an Arabic word passed through medieval Latin.
What we use it for
The largest use of antimony is as antimony trioxide in flame retardants. On its own it does little, but combined with chlorine or bromine compounds in plastics, textiles and electronics it interrupts the chemical reactions of burning and helps materials meet fire safety standards. Children's clothing, seat covers and television casings often contain it.
In metallurgy, a few per cent of antimony added to lead makes the alloy much harder and stiffer. This is used for the grids in lead-acid batteries, for bullets and shot, and historically for the type metal used in printing. Antimony is also alloyed into pewter and some solders. In electronics, indium antimonide and related compounds serve as infrared detectors, and antimony is a dopant that adjusts the conductivity of silicon. Antimony compounds appear in some glass and ceramic pigments and as a catalyst in making PET plastic bottles.
Reading the numbers
Antimony melts at about 631 °C and boils at about 1635 °C. Its melting point is modest for a metallic element, similar to that of aluminium. Its density of 6.70 grams per cubic centimetre makes it lighter than iron and slightly under seven times as dense as water.
Its electron configuration, [Kr] 4d10 5s2 5p3, gives five outer electrons. That places antimony in group 15 under arsenic and above bismuth, in the same column as nitrogen and phosphorus. Like its neighbours it forms compounds in the +3 and +5 states, and its electronegativity of 2.05 is close to the midpoint between typical metals and non-metals, which is exactly what its metalloid label means. Its first ionisation energy of 834 kilojoules per mole is higher than that of most metals. A rare property is that antimony expands slightly as it solidifies, which is why antimony alloys make such sharp castings.
Safety and the environment
Antimony is toxic, though less so than its neighbour arsenic. Its compounds irritate the skin, eyes and lungs, and long-term exposure damages the heart, liver and lungs. Antimony potassium tartrate, once used as a medicine to induce vomiting, is now avoided for that reason. Because antimony trioxide is used to make PET plastic, tiny traces can leach into bottled water, especially if bottles are stored warm, though levels are normally far below safety limits.
Mining and smelting release antimony into water and soil around production sites, and stibnite tailings can contaminate rivers. The brominated flame retardants that antimony works alongside have raised environmental concerns of their own, which has driven research into alternatives.
Did you know?
- Stibnite, antimony's main ore, was ground up and used as kohl eye make-up in ancient Egypt.
- Antimony is one of the few substances that expands when it freezes, a property shared with water, bismuth and gallium.
- The Xikuangshan mine in Hunan, China, has for over a century been the largest antimony source on Earth.
- Adding a few per cent of antimony to lead makes the soft metal hard enough to hold its shape as a battery plate or bullet.
- Antimony is brittle enough to shatter if struck with a hammer, despite looking like a typical metal.
More in the metalloids
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 7 metalloids on one page, or browse all 118 elements.
Compare Antimony with another element
Each comparison has a side-by-side data table and a plain-English summary of the differences.
Frequently asked questions
Is antimony a metal?
It is classed as a metalloid. Antimony has the shiny grey look of a metal, but it is brittle rather than malleable, conducts electricity poorly, and forms compounds in the way non-metals such as phosphorus do. It sits on the diagonal boundary between metals and non-metals in the periodic table.
Is antimony toxic?
Yes. Antimony and its compounds are poisonous, causing stomach upset, heart and liver damage and lung irritation, though it is less toxic than arsenic. Exposure is mainly a workplace concern; everyday contact with antimony in flame-retardant plastics or PET bottles involves very small amounts.
What is antimony used for today?
Most goes into antimony trioxide, which is added to plastics and textiles as part of flame retardant systems. The next largest use is hardening lead for the grids in lead-acid car batteries. Smaller amounts go into bullets, pewter, glass, pigments and semiconductors.
Why is antimony's symbol Sb?
The symbol comes from stibium, the Latin name for the black antimony sulfide mineral stibnite that was used as eye make-up. The name antimony itself has a different, uncertain origin, probably via Arabic and medieval Latin.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Antimony reference article. Spotted an error? Tell us.