Antimony Uses & Why It’s a US Critical Mineral

Antimony is a metallic element used mainly as a flame retardant synergist and as a hardener in lead alloys, and the United States has designated it a critical mineral because domestic mine production is essentially zero while defense, aerospace, and battery industries depend on imported supply. This article explains what antimony is used for, why the US classifies it as critical, and how its supply chain works.

What Is Antimony?

Antimony (chemical symbol Sb, from the Latin stibium) is a brittle, silvery-gray metalloid that has been known since ancient times. It occurs naturally in over 100 minerals, but the only commercial ore is stibnite (antimony sulfide, Sb₂S₃). China is by far the largest producer, accounting for roughly half of global mine output, followed by Russia, Tajikistan, and Myanmar. The US has not mined antimony since the 1990s, though it does have small deposits in Alaska, Idaho, Montana, and Nevada.

Primary Uses of Antimony

Antimony’s unique properties—it expands when it cools, resists flame, and hardens alloys—make it valuable in several industries:

• Flame retardants (about 50% of consumption): Antimony trioxide (Sbâ‚‚O₃) is added to plastics, textiles, and adhesives. It works synergistically with halogenated compounds to suppress fire by interfering with free-radical reactions in the flame.
• Lead-acid batteries (about 30%): Antimony hardens lead and improves the charge/discharge cycle life of battery grids, especially in industrial and vehicle batteries.
• Alloys: Antimonial lead is used in ammunition, cable sheathing, and solder. It increases hardness and reduces creep.
• Glass and ceramics: Antimony compounds act as fining agents to remove bubbles and as opacifiers in enamels and glass.
• Semiconductors: Indium antimonide and other III-V compounds are used in infrared detectors and Hall-effect sensors.
• Medicinal (historic): Antimony compounds were once used as emetics and in the treatment of parasitic infections; some are still used in veterinary medicine.

Why Is Antimony a US Critical Mineral?

The US Geological Survey (USGS) defines a critical mineral as one that is essential to economic or national security and whose supply chain is vulnerable. Antimony meets both criteria:

• No domestic mine production: The US relies entirely on imports, mostly from China, which also refines a large share of global supply.
• Defense and aerospace demand: Antimony is used in armor-piercing ammunition, night-vision goggles, infrared optics, and flame-retardant materials for military equipment.
• Renewable energy and batteries: Antimony is a component in some flow batteries and in lead-acid batteries used for grid storage, linking it to clean energy transitions.
• Low substitution potential: For many applications, no cost-effective substitute exists, especially in flame retardants and certain alloys.

In 2018, the US Department of the Interior published a list of 35 critical minerals that included antimony. The list was updated in 2022 to add nickel and zinc, but antimony remained. The designation triggers federal actions such as permitting support, research funding, and stockpiling through the Defense Logistics Agency.

How Is Antimony Processed?

Processing antimony ore typically involves the following steps:

1. Mining: Stibnite is extracted via underground or open-pit methods.
2. Concentration: Ore is crushed and floated to produce a concentrate containing 30–60% antimony.
3. Smelting: The concentrate is roasted to produce antimony trioxide, or smelted with iron scrap to produce crude antimony metal.
4. Refining: Crude metal is further purified by electrolysis or liquation to achieve commercial grades (typically 99.65% Sb).

The choice of pyrometallurgical vs. hydrometallurgical methods depends on ore grade and impurities. China dominates both mining and refining, so even if a country mines antimony, it often sends the concentrate to China for processing.

Common Problems and Misconceptions

One common misconception is that antimony is a rare metal. In fact, it is about as abundant as tin, but it is rarely concentrated enough to mine economically. Another issue is the environmental and health impact: antimony trioxide is classified as a possible human carcinogen (IARC Group 2B), and mining areas can suffer from arsenic and sulfur contamination. This has led to stricter regulations and higher costs in some regions.

Another problem is the volatility of supply. China’s export quotas and environmental crackdowns have caused price spikes in the past. The US has tried to mitigate this by stockpiling antimony and funding research into recycling from lead-acid batteries and flame-retarded plastics, but recycling rates remain low.

Alternatives and Substitutes

For flame retardants, alternatives include aluminum hydroxide, magnesium hydroxide, and organophosphorus compounds, but they often require higher loadings or have different fire-performance characteristics. In lead-acid batteries, calcium and selenium can replace antimony in some grid alloys, but antimony is still preferred for deep-cycle batteries. In ammunition, tungsten and steel are used for non-lead alternatives, but they lack the density and hardness of antimonial lead. In glass, tin oxide and cerium oxide can replace antimony as fining agents, but they are more expensive. Overall, no single substitute covers all applications, which is why antimony remains critical.

Frequently Asked Questions

Is antimony dangerous to humans?

Antimony compounds can be toxic. Acute exposure causes nausea, vomiting, and diarrhea; chronic exposure can affect the heart and lungs. The US Occupational Safety and Health Administration (OSHA) sets a permissible exposure limit of 0.5 mg/m³ for antimony and its compounds. However, metallic antimony is less toxic than its soluble compounds.

Can antimony be recycled?

Yes, but recycling is limited. The main sources are lead-acid battery scrap and antimony-containing residues from smelting. In the US, recycling of lead-acid batteries recovers some antimony, but it is often downcycled into lower-grade alloys. The USGS estimates that only about 15% of antimony consumption is from secondary sources.

Why is antimony called a critical mineral but not a rare earth?

Critical minerals include both rare earths and non-rare metals like antimony, lithium, and cobalt. The term “rare earth” refers specifically to the 17 lanthanide elements plus scandium and yttrium. Antimony is a metalloid, not a rare earth, but it is critical because of supply risk and essentiality.

What is the price of antimony?

Antimony prices fluctuate widely. As of 2025, antimony metal trades around $20,000–$30,000 per metric ton, but prices have spiked above $40,000 during supply disruptions. For current prices, check commodity exchanges like the London Metal Exchange (LME) or the Shanghai Metals Market.

Does the US have any antimony mines?

There are no active antimony mines in the US as of 2025. The Stibnite Gold Project in Idaho, proposed by Perpetua Resources, aims to produce antimony as a byproduct of gold mining, but it is still in the permitting stage. If approved, it could supply about 35% of US demand.

What is the difference between antimony and arsenic?

Both are metalloids in group 15 of the periodic table, but antimony is heavier and more metallic. Arsenic is more toxic and is used mostly as a wood preservative and in semiconductors. Antimony’s main uses are flame retardants and battery alloys. They are often found together in ores, which complicates processing.

Related

• Electric Water Heater Calculator: What It Can Estimate
• Capacitor Voltage From Current: Formula and Example
• Mac Start Up Automatically After Power Failure?

in t | Total time | min | 60 | 0
in d | Distance | km | 10 | 0 | 100000
out pace | Average pace | min/km | t / d | 2
out speed | Average speed | km/h | d / (t / 60) | 2