Rock Sulfur and Raw Sulfur: Sources, Uses, Price Data

Rock sulfur is native sulfur: the element S found as a bright yellow, soft mineral around volcanic vents and in some salt-dome and evaporite deposits. Raw sulfur is the trade name for unrefined elemental sulfur, and today most of it is not dug up at all. The U.S. Geological Survey (USGS) estimated that U.S. plants recovered 7.6 million tons of elemental sulfur in 2025, at petroleum refineries, natural-gas plants and coking plants (USGS Mineral Commodity Summaries 2026). About 90% of the sulfur consumed in the United States goes into sulfuric acid.

This page sorts out the terms people search for (rock sulfur, sulfur rock, raw sulfur, sulphur rock, sulfur minerals), explains whether sulfur is a rock, shows where each form comes from, lists seven real uses, and gives dated price data and a small calculator. Both spellings are in use: sulfur in the United States and sulphur in the United Kingdom, Australia and much of Africa. They mean the same element.

What is rock sulfur, and is sulfur a rock?

Sulfur is a mineral, not a rock. A mineral is a natural substance with a fixed chemical makeup and crystal structure. A rock is a mix of minerals. Sulfur occurs as a native element (it is found uncombined), so geologists classify it as a native-element mineral with the formula S. A lump of yellow crystals in volcanic rock is “rock sulfur” in everyday speech, and a rock that holds enough sulfur to mine is called sulfur ore.

The mineral is easy to recognise. It is lemon yellow to yellow-brown, has a Mohs hardness of 1.5 to 2.5 (a fingernail can scratch it), a specific gravity of 2.0 to 2.1 (about twice the weight of water), melts at about 115 degrees Celsius and burns with a blue flame that is hard to see in daylight (Geology.com; Minerals Education Coalition). Burning produces sulfur dioxide, a gas with a sharp smell. The name is said to mean “burning stone”.

Is sulfur found in rocks?

Yes, but mostly locked inside other minerals rather than as yellow crystals. Sulfur is rarely found pure at the Earth’s surface; as an element it is an important part of sulfate and sulfide minerals (Geology.com). Sulfides combine sulfur with metals: pyrite (iron sulfide), galena (lead), chalcocite (copper) and sphalerite (zinc) are the common ore minerals (Minerals Education Coalition). Sulfates combine sulfur with oxygen; gypsum, calcium sulfate with water in its structure, is the best-known one.

The sulfur percentages in the table come from the chemical formulas (FeS2 and CaSO4 with two water molecules) and the atomic weights of the elements. Real ore and gypsum runs a little lower because of impurities.

Raw sulfur: where it comes from

Raw sulfur used to be a mining product. Today the vast majority is a by-product of oil refining and natural-gas processing (Minerals Education Coalition). Crude oil and sour gas contain sulfur compounds that must be removed to meet fuel and pipeline rules, and the plant converts them to elemental sulfur that it sells as a side product. USGS counted 31 companies recovering elemental sulfur at 81 plants in 25 U.S. states in 2025, with Louisiana and Texas making about 54% of domestic output (USGS, 2026).

Infographic

The Frasch process in 4 steps

1. 1Drill to the depositA well is drilled into a salt-dome or bedded sulfur deposit.
2. 2Inject hot waterHot water is forced into the deposit and melts the sulfur (it melts at about 115 degrees Celsius).
3. 3Pump to surfaceThe molten sulfur is pushed up the well.
4. 4Cool or shipIt is left to solidify or shipped as a liquid.

That has a practical result for anyone buying or financing a sulfur-based business: supply follows fuel production, not sulfur demand. When refineries run hard, sulfur is plentiful whatever the price. USGS says reserves of sulfur in crude oil, natural gas and sulfide ores are large and supplies should be adequate for the foreseeable future.

How native sulfur is mined

Where native sulfur is mined, three methods are used: conventional underground mining, conventional surface mining, and the Frasch process, which melts the sulfur underground (Minerals Education Coalition). Mined sulfur is mostly from salt domes (large underground salt bodies with sulfur in the surrounding rock) or from bedded evaporite deposits laid down when ancient seas dried up. Volcanic sulfur is the third source.

Kawah Ijen in East Java, Indonesia, is the best-known volcanic case. A report in the Yale Journal of International Affairs describes 350 to 400 miners quarrying sulfur by hand there each year, carrying 70 to 90 kilograms per trip up the crater wall (Yale Journal of International Affairs). It is small in output next to refinery sulfur.

Seven uses of rock sulfur and raw sulfur

Sulfur is rarely used as the element. It is burned to sulfur dioxide and converted to sulfuric acid, then the acid is used. These are the seven largest or most useful end uses, in no strict order.

1. Sulfuric acid. About 90% of sulfur consumed in the United States is used as sulfuric acid (USGS, 2026).
2. Phosphate fertilizer. Sulfuric acid breaks down phosphate rock to make fertilizer; sulfur’s main use is in chemicals for agriculture, mostly fertilizers (Minerals Education Coalition). USGS links lower phosphate rock use in 2025 to slightly lower sulfur needs.
3. Metal leaching. Acid dissolves metal from ore, and in nickel high-pressure acid leaching (HPAL) plants sulphuric acid is typically made by burning sulphur on site (Argus Media, February 2026).
4. Petroleum refining. Acids and sulfur compounds are used in refining, and refineries are also the main source of the sulfur.
5. Rubber and chemicals. Vulcanised rubber for tyres and many organic and inorganic chemicals need sulfur at some stage.
6. Crop protection and pharmaceuticals. Insecticides, fungicides, pharmaceuticals, soaps, paper and dyes use sulfur compounds (Geology.com).
7. Direct soil use. Elemental sulfur lowers soil pH and supplies plant sulfur, but only after soil microbes convert it to sulfate (covered below).

Who produces the world’s sulfur

World production of sulfur in all forms was 84 million metric tons in 2025, and China alone made about 19 million (USGS, 2026). Output tracks refining and gas processing, so the top producers are big fuel economies and Gulf states. USGS puts world resources of elemental sulfur in evaporite and volcanic deposits, plus sulfur in gas, oil, tar sands and metal sulfides, at about 5 billion tons, and says the sulfur in gypsum and anhydrite is almost limitless.

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Largest sulfur producers, all forms

Million metric tons, 2025 estimate, seven largest listed producers

What drove sulphur prices up

Sulfur is cheap in a normal year and very costly in a shortage. USGS reports the average U.S. plant price rising to US$180 per metric ton in 2025 from US$46.42 in 2024, which made 2025 shipments worth about US$1.4 billion, US$1 billion more than in 2024 (USGS, 2026). In 2026 the price climbed much further as shipping from the Middle East through the Strait of Hormuz was disrupted.

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2026 sulphur price moves in three benchmarks

US$ per tonne (Tampa: per long ton, delivered; Qatar and Kuwait: fob); Tampa 2Q to 3Q, Qatar June to August, Kuwait July to August

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U.S. average plant price of elemental sulfur

US$ per metric ton, average unit value at mine or plant

Argus Media reported that the third-quarter 2026 contract for molten sulphur delivered into Tampa, Florida settled at a record US$705 per long ton (a long ton is 2,240 pounds, about 1.016 metric tons), up US$50 from the US$655 agreed for the second quarter. Spot exports from U.S. Gulf refineries were assessed at US$1,100 to US$1,150 per metric ton on 9 July 2026 (Argus Media, 13 July 2026; Fertilizer Daily, 15 July 2026). Monthly Middle East prices (fob, loaded at the port) were also high, though below the US Gulf spot level: QatarEnergy kept its August price at US$890 per tonne, and Kuwait’s KPC cut its August price to US$865 from US$950 in July (Argus, 30 July 2026; Argus, 4 August 2026).

Why buyers outside fertilizer feel it too

Nickel HPAL plants in Indonesia burn sulphur to make acid. Argus assessed granular sulphur delivered to Indonesia at US$542.50 per tonne on 5 February 2026, up 196% from January 2025, and said Indonesia imported 5.35 million tonnes in 2025, 48% more than a year earlier (Argus Media, 12 February 2026). Argus also noted that U.S. Gulf cargoes reached east African copper-belt consumers in the second quarter. The price quoted depends on the place and the form, so always check whether a number is FOB (loaded onto the ship at the port), delivered, liquid or solid. A weekly index is the right tool for a live number; this page gives dated reference points only.

Acid cost calculator: from sulfur price to cost per tonne of acid

The calculator below turns a sulfur price into a raw-material cost per tonne of sulfuric acid. One tonne of sulfur can make at most about 3.06 tonnes of pure sulfuric acid, the ratio of the molecular weight of H2SO4 (98.08) to the atomic weight of sulfur (32.06). Real plants convert less than 100%, so the efficiency is an input.

Elemental sulfur versus gypsum in soil

Farm use is a real but smaller part of the story. Plants take up sulfur as sulfate. Elemental sulfur can be applied, but the sulfur must first be oxidized by soil organisms to sulfate, so it should be finely ground and applied early in the season, and sulfate sources are likely better choices (North Carolina State Extension, 2026). The same guide lists elemental sulfur at 88 to 100% sulfur and gypsum (land plaster) at 17 to 20% sulfur, which is why a tonne of gypsum delivers far less sulfur than a tonne of the element. Over-application of elemental sulfur acidifies soil, so follow a soil test.

Sulfur minerals, acid drainage and mining

The same chemistry that makes sulfur useful makes sulfide waste a risk. When pyrite is exposed to air and water it oxidizes to ferric hydroxide and sulfuric acid; water with a pH below 6.0 and acidity above alkalinity is classed as acid mine drainage (AMD) (Kentucky Energy and Environment Cabinet). Kentucky’s abatement program treats it by raising pH with an alkaline reagent such as calcium or sodium, aerating water so metals settle out, using settling ponds and building wetlands, usually in combination. Finding the sulfide rock before disturbing it is the cheapest control, because waste rock can be placed and capped on purpose.

▶ A claymation explainer on the seven environmental impacts of mining. · 2:31

Handling and sampling: safety notes

Sulfur is flammable, so keep dust and molten sulfur away from ignition. Hydrogen sulfide, the rotten-egg gas given off by sulfur deposits, vents and sour-gas plants, is one of the leading causes of workplace gas inhalation deaths in the United States, with 46 worker deaths recorded between 2011 and 2017. It is heavier than air, collects in low spots and confined spaces, and quickly stops being smelled, so smell is not a safe alarm (OSHA). Visit a volcanic or sour-gas site only with permission, a gas monitor and training. Never test or dig on someone else’s claim or protected land.

How sulfur and sulfide ground is found

Surface yellow staining, altered rock and gossans (rusty caps over sulfide bodies) are the field clues, followed by sampling and drilling. Satellite screening can map surface alteration over a large licence before a crew goes out, which narrows where to sample; it does not give a sulfur grade or a resource estimate. Farmonaut offers satellite-based mineral detection that lists gypsum among its industrial minerals, and you can submit an area for a quote. For a wider view of sulfur ore, see our guide to sulfur and sulfur ore trends.

▶ A short explainer on how AI is used in mineral exploration and whether it finds mines. · 4:37

Frequently asked questions

Is sulfur a rock or a mineral?

Sulfur is a mineral. It is a native element with the formula S. A rock is a mix of minerals, so a sulfur-rich rock is sulfur ore, not “sulfur” itself.

What is rock sulfur used for?

Almost all of it is turned into sulfuric acid, which makes phosphate fertilizer and leaches metals such as nickel from ore. Small amounts go to rubber, chemicals, crop protection and direct soil use.

What is raw sulfur?

Raw sulfur is unrefined elemental sulfur, usually recovered from oil and gas processing and sold as molten liquid or solid prills or lumps.

Is sulfur found in rocks?

Yes. It sits in sulfide minerals such as pyrite and in sulfate minerals such as gypsum, and appears as native yellow crystals near volcanic vents.

Where is native sulfur mined?

From salt-dome and evaporite deposits using the Frasch process or conventional mining, and by hand at volcanic sites such as Kawah Ijen in Indonesia (Minerals Education Coalition; Yale Journal of International Affairs).

How much does sulfur cost per tonne?

It varies by market and date. The USGS 2025 average U.S. plant value was US$180 per metric ton, the Tampa third-quarter 2026 contract was US$705 per long ton, and Middle East monthly prices were US$865 to US$890 per tonne in August 2026 (sources above).

Is elemental sulfur good for soil?

It lowers pH and supplies sulfur after soil organisms convert it to sulfate, which takes time. Gypsum and ammonium sulfate act faster (North Carolina State Extension).

Is sulfur dangerous?

The solid is low-toxicity but flammable, and burning it gives sulfur dioxide. The bigger hazard at deposits and gas plants is hydrogen sulfide, which can overcome workers quickly (OSHA).

Why does pyrite cause acid mine drainage?

Pyrite reacts with air and water to form sulfuric acid and iron hydroxide, which lowers water pH and dissolves metals. Treatment adds alkaline reagent, aerates, settles and uses wetlands (Kentucky Energy and Environment Cabinet).

Can sulfur be found by satellite?

Satellites map surface alteration and rock types that point to sulfide or sulfur-bearing ground. Samples and drilling are still required to prove sulfur content.