How Is Sulfur Mined? 7 Extraction Methods Compared

Sulfur is mined in only a few places today. Most sulfur mining has given way to recovery: refineries and gas plants strip the element out of fuel, and smelters capture it as acid. USGS puts world output of sulfur in all forms at about 84 million metric tons in 2025, and it says most of that supply comes from processing fossil fuels. The three true mining routes are hot-water melting (the Frasch method), surface pits and underground workings, as the Minerals Education Coalition lists them. Volcanic vents add a small, hand-worked trade.

This guide compares seven ways sulfur (or sulphur, in UK and Australian spelling) reaches the market: what each one starts from, how it works, where it runs and what can go wrong. It is written for consultants and project owners who need to explain why a sulfur “mine” is rarely what a client pictures.

How is sulfur mined and recovered: the seven methods at a glance

The table compares the methods by feedstock, product and main site risk. It gives no cost per tonne, because no public source we opened publishes a like-for-like cost across all seven. Costs depend on the site, on fuel and on who pays for the plant.

How we chose: we included every route named by USGS or the Minerals Education Coalition that yields sulfur at commercial scale, plus vent collection because it is the image most people have of sulfur mining. The order runs from true mining to recovery. It is not a ranking of quality.

Why most sulfur is no longer mined

Recovered sulfur is a byproduct of making fuel, so its supply does not depend on sulfur demand. Refineries and gas plants keep producing it whatever the sulfur price. Frasch mines, which have to pay for every tonne they melt, could not match that. The history of the Frasch process shows byproduct recovery lowering prices from the 1970s and pushing many of those mines out of business.

Chart

US sulfur output by form

Thousand metric tons; 2025 is an estimate

The US numbers make the point. USGS reports 81 elemental sulfur plants in 25 states in 2025, listed in descending tonnage as petroleum refineries, natural gas plants and coking plants. Five nonferrous smelters made byproduct acid, about 6% of output. Louisiana and Texas made about 54% of the elemental sulfur. No US mine appears in that list.

Output by country therefore follows refining, gas and smelting more than geology. USGS warns that the sulfur in Saudi crude, for example, may be recovered at a refinery in the United States, so a country’s output says little about its rocks.

Sulfur mining methods: the three true mining routes

1. Frasch process: melting sulfur underground

Best for: native sulfur in permeable layers, sealed above and below by tighter rock.

Herman Frasch brought the first molten sulfur to the surface in Louisiana on 24 December 1894, using pipes to get past quicksand above a salt dome. A well holds three pipes, one inside another. Water at about 165 °C and 2.5 to 3 MPa goes down the outer pipe and melts the sulfur, which melts near 115 °C. The molten sulfur flows into the middle pipe. Hot air from the inner pipe froths it so it can rise.

Pros: no pit and no ore haulage, and the product can reach 99.7 to 99.8% sulfur when it is not contaminated by organic matter. Cons: it burns a lot of fuel to heat water, and it only suits the right geology. Fuel cost held the method back until Spindletop oil made fuel cheap in the early 1900s. The last US Frasch mine closed in 2000, and that same undated source lists Mexico, Ukraine and Poland as places still using it. We did not find an operator report to confirm this.

2. Surface mining of native sulfur

Best for: shallow native sulfur (sulfur in its pure element form, not bound in another mineral) where little waste sits on top.

The steps resemble any small open pit: strip the overburden (the waste rock above the ore), drill and blast if needed, dig, then haul the ore to a plant that separates the sulfur, usually by melting it. The largest native accumulations sit in the subsurface, tied to gypsum and anhydrite that bacteria altered, so few deposits are shallow enough for this route.

Pros: simple equipment and easy to inspect. Cons: sulfur dust burns and a fire gives off sulfur dioxide, so dust and ignition control come first. Exposed sulfide minerals can also raise acid drainage risks. The ore also has to compete with recovered sulfur on price.

3. Underground mining of native sulfur

Best for: richer, deeper native ore that will not take hot water well, for example tight rock that cannot carry the melt to a well.

The conventional underground route uses shafts or declines (sloping tunnels) with normal underground ore extraction, then the same melting plant as a pit. Pros: a small surface footprint. Cons: high cost per tonne against recovered sulfur, plus ground support, ventilation and fire control. Hydrogen sulfide may also occur around evaporite-hosted sulfur, so gas testing belongs in any underground plan.

Sulfur mines at volcanoes: collecting sulfur from vents

4. Volcanic vent collection

Best for: very small local supply. It is not a route a new project should plan on.

Native sulfur forms near volcanic vents as hot gases cool. Ijen, in East Java, Indonesia, is the best-known working example. Ceramic pipes channel vent gas until molten sulfur condenses, and workers break up the cooled yellow solid. Reported loads run 75 to 90 kg, carried about 300 m up to the crater rim. The same source gives about 200 miners taking 14 tons a day, with pay near US$13 a day as of September 2010, and it records respiratory complaints and poor protective gear.

Pros: almost no capital. Cons: serious worker health risks and tiny volume. At 14 tons a day, a full year of work would be around 5,000 tons, which is about 0.006% of world output.

Sulfur extraction process at refineries and gas plants

This is where the bulk of sulfur comes from. Gas-treating units first pull hydrogen sulfide (H2S, a toxic gas) out of the fuel stream. A Claus plant then turns that gas into liquid sulfur.

Infographic

From sour gas to liquid sulfur in 5 steps

1. 1SeparatePull H2S out of the fuel stream.
2. 2BurnTurn about one third of the H2S into sulfur dioxide.
3. 3CondenseDrain off the first 60 to 70% of the sulfur.
4. 4ReactPass remaining gas over catalyst beds and condense again.
5. 5TreatBurn or further clean the tail gas.

5. Refinery recovery with the Claus process

Best for: the steady, low-cost supply that sets the market.

Patented in 1883, the Claus process has two stages. In the furnace, the gas burns at above 850 °C with limited air, so that only about one third of the H2S becomes sulfur dioxide. That stage already yields 60 to 70% of the final sulfur. In the catalyst beds, the remaining H2S reacts with the sulfur dioxide over an aluminum or titanium oxide catalyst. Each bed is followed by a condenser that drains off liquid sulfur. Tail gas, the small stream left over, is burned or sent to further treatment.

Pros: uses gas that already has to be treated, and the plant runs alongside existing units. Cons: output follows refinery runs and not sulfur demand, and it needs strict control of toxic gas. Argus reported in July 2026 that some US Gulf producers cannot export solid sulfur and depend on local liquid buyers, so weak local demand is a concern for them.

6. Sour gas plant recovery

Best for: regions with sour gas (natural gas high in H2S).

The chemistry matches the refinery route. The main difference is the feed: gases with over 25% H2S suit a straight-through Claus plant, while leaner gases need a split-flow layout or preheating. Pros: large and long-lived supply. Cons: output is tied to gas field life, and remote plants need rail or port access to reach buyers. US coking plants also recover some sulfur, on a smaller scale, according to USGS.

Sulfur recovery from metal smelters

7. Smelter acid capture

Best for: copper, zinc, lead and nickel smelters that have nearby acid buyers.

Sulfide ore concentrates hold a lot of sulfur. EPA’s AP-42 chapter gives about 25% sulfur in copper concentrate and says roasting at about 650 °C can remove 20 to 50% of it as sulfur dioxide. Smelting and converting release more. Instead of venting that gas, plants clean it and feed it to a sulfuric acid plant, which works in the same way as the contact process: vanadium catalyst, then absorption.

According to the same EPA chapter, single-contact plants convert 92.5 to 98% of the gas, and double-contact plants collect from 98 to over 99%. Pros: turns a pollutant into a saleable product. Cons: the smelter has to sell or move acid whatever the market does, and acid is costly to ship. EPA notes that short-term sulfur dioxide exposure can harm breathing, so capture rates matter to neighbors and to permits. For nearby topics, see our guides to zinc mining and copper mines in the DRC, where acid supply affects leaching.

Sulfur production by country and the US trend

China leads USGS’s 2025 estimates at 19 million tons in all forms, ahead of the United States at 8.1 million. The chart shows selected large producers. These are all-forms figures, so they mix elemental sulfur and byproduct acid, and they include sulfur made from imported crude.

Chart

Selected large sulfur producers

Million metric tons, all forms, 2025 estimates; selected countries

US output has eased slowly. USGS estimates 7.6 million tons of recovered elemental sulfur in 2025, down from 8.01 million in 2022 and 2023. Other forms, mostly byproduct acid, were about 500,000 tons. USGS expected smelter maintenance to trim acid output in 2025.

What sulfur sells for and why it moves

Sulfur prices swing widely because supply barely responds to price. USGS records the Tampa contract at US$116 per long ton in early 2025, rising to US$310 by early October 2025. Argus then reported the third-quarter 2026 settlement at a record US$705 per long ton, up from US$655, as Middle East shipments fell away. US Gulf spot exports were assessed at US$1,100 to US$1,150 per tonne on 9 July 2026.

Chart

Tampa sulfur contract settlements

US$ per long ton, delivered; selected dates, not a full series

A yuan-priced benchmark has since eased. Trading Economics showed 6,669 CNY per tonne on 15 October 2026, down 13.43% over a month yet 141.83% above a year earlier. These are different markets and dates, so do not compare them directly. Check a current quote before using any of them in a model.

Demand comes mainly from acid. USGS says about 90% of US consumption is in the form of sulfuric acid. Worldwide, The Fertilizer Institute says about 90% of sulfur becomes acid, and 60 to 75% of that acid goes to phosphate fertilizer, and more than half of global sulfur is traded across borders. Metal leaching is the other growing draw: Argus reported that Indonesia’s nickel sector imported 5.35 million tonnes of sulfur in 2025, 48% more than a year earlier. Our guide to sulfur uses covers these markets, and this review of sulfur ore trends looks at the wider industry.

How to judge a sulfur mining project

For an owner or consultant, the price spike makes native sulfur look attractive. These checks test whether it would still work when prices fall.

1. Confirm the host rock. Native sulfur sits mainly in salt dome cap rock and evaporites. See our guide to types of ore deposits for how deposit style drives method and grade.
2. Separate native sulfur from sulfide sulfur. A “high sulfur” assay may only mean pyrite (iron sulfide). Pyrite cannot go through a Frasch well or a simple melter.
3. Test permeability early if Frasch is the plan. Hot water has to reach the sulfur and stay contained.
4. Price the heat. Fuel decided the fate of the early Frasch mines, so model water heating at your local fuel price.
5. Run the model at low prices. The US average plant value was just US$46.42 per metric ton in 2024, against an estimated US$180 in 2025 (USGS, 2026). A project that needs a price of several hundred dollars is betting against recovered supply.
6. Map the route to a buyer. Liquid sulfur needs heated transport, and solid sulfur needs forming and port handling.
7. Plan for gas, fire and acid drainage from the start, and check permits with the regulator.

Use a margin check alongside these steps. Satellite screening can help with early desk work on the ground around a project. Farmonaut’s satellite-based mineral detection lists materials such as gypsum, copper and zinc; sulfur is not a listed target, and any such results are exploration targets ahead of drilling, not a resource estimate. For a project discussion, use the quote form or contact the team.

▶ Remote sensing for mining explained in plain words (2:01) · 2:01

Sulfur extraction safety and environmental controls

Every method above shares a few hazards. The controls differ by site, so treat this as a checklist for discussion and not as a plan.

• Toxic gas: H2S at recovery plants and possibly in native sulfur workings. Use fixed and personal monitors, and rescue procedures.
• Sulfur dioxide: from burning sulfur, smelters and tail gas. EPA lists metal extraction from ore among smaller SO2 sources, behind fossil fuel burning.
• Fire and dust: sulfur burns easily, so control dust, sparks and storage.
• Molten sulfur: pipes and tanks need heating and burn protection.
• Water: Frasch wells need containment, and exposed sulfide rock can generate acid drainage. Ijen’s acidic crater lake shows the natural version: its outflow harms the downstream river.
• Closure: a plan for wells, pits and waste belongs in the first budget.

▶ The seven environmental impacts of mining, explained in clay (2:31) · 2:31

Frequently asked questions

How is sulfur mined?

Native sulfur is mined three ways: melting it underground with hot water (Frasch), surface pits and underground workings. Most supply is not mined at all, as it is recovered from oil, gas and smelter gases.

How is sulphur mined in the UK and Australia?

The term is just the local spelling, and the methods are the same. USGS lists Australia at about 900,000 tons of output in all forms in 2025, a figure that covers recovered forms as well as any mined sulfur.

How do you extract sulfur from natural gas?

The plant separates H2S from the gas, then burns part of it in a Claus furnace. The remainder reacts over a catalyst to give liquid sulfur, and the leftover tail gas goes to treatment.

What is the Frasch process?

It is a well-based method. Superheated water melts native sulfur underground, and compressed air lifts the froth to the surface. It dates from 1894.

Are there still sulfur mines in the United States?

The last US Frasch mine closed in 2000. USGS’s 2025 production summary lists refineries, gas plants, coking plants and smelters, and no mines.

Where are sulfur mines located?

The Frasch process is reported as still used in Mexico, Ukraine and Poland. Hand collection continues at Ijen in Indonesia. Output by country mostly reflects refineries and gas plants.

Can you mine sulfur at home or on a claim?

Do not try small-scale extraction. Burning or melting sulfur gives off toxic gas and has a fire risk. Any work on a claim needs a license, landowner permission and a site safety plan.

What is the most sustainable sulfur extraction method?

No source we opened scores all seven on one scale. Recovery removes sulfur that would otherwise reach the air or fuel, which is a strong argument for it, but those plants still handle toxic gas and need their own permits.

How much sulfur is produced each year?

USGS estimates about 84 million tons of sulfur in all forms in 2025, against 83.9 million in 2024.

How much acid does a tonne of sulfur make?

About 3.06 tonnes of pure sulfuric acid in theory, from the atomic masses. Real plants yield a little less because of losses.

Bottom line

Sulfur mining survives in a few places, but recovery supplies the market. Anyone assessing a native sulfur project should test it at low prices, confirm the sulfur is native and not sulfide, and find a buyer with a working route. The recent record prices came from a supply shock, and they are no proof of a long-term floor.