Iran holds the largest gilsonite deposits outside the United States, and for most of the world it is the practical source of supply. The veins that matter run through Kermanshah and Ilam in the west of the country, where hydrocarbon purity reaches 98 per cent — high enough for drilling fluid and asphalt modification without further refining. Not every Iranian deposit is that good, and knowing which mine a cargo came from matters more than any single figure on a certificate.
RAHA Gilsonite Co. owns gilsonite rock mines in Iran and supplies the material as lump and as powder in a range of mesh sizes. This page sets out where Iran’s gilsonite actually comes from, why the mine of origin changes what the material can be used for, how Iran compares with the Utah deposits, and the technical detail a buyer needs before contracting.
Where Iran’s gilsonite comes from
Gilsonite is a naturally occurring solid hydrocarbon of the asphaltite class, formed where petroleum seeped into fractures in the earth’s crust and solidified there. In Iran it occurs as near-vertical veins filling fissures in calcareous shale, limestone and sandstone.
The deposits are not uniform, and this is the single most important thing to understand before buying Iranian gilsonite.
| Mine region | Hydrocarbon content | What it is used for | Notes |
|---|---|---|---|
| Kermanshah — Gilan-e Gharb, Qasr-e Shirin | Highest, up to 98% | Drilling fluid, asphalt modification, ink, paint | The first-quality material and the volume export grade |
| Ilam — toward the Iraq border | High, comparable to Kermanshah | Drilling fluid, asphalt modification | Same vein system, same grade class |
| Kuhdasht, Lorestan | Markedly lower | Foundry sand additive only | Not suitable for drilling or asphalt work |
Why this matters commercially. Lorestan material and Kermanshah material are both sold as “Iran gilsonite”. They are not interchangeable. A drilling contractor who receives Lorestan ore against a Kermanshah specification will see the fluid loss figure fail, and the cost of that failure on a rig is many times the price difference on the clay. Ask every supplier which mine the cargo comes from, and ask for it in writing on the contract rather than only on the certificate.
The vein system
The Iranian veins are large. They range from a few metres to around twenty metres in width and from a few kilometres to thirty or forty kilometres in length, with some believed to extend to fourteen hundred metres in depth. At the surface the dikes run from a few millimetres to more than five metres thick; some are exposed for up to thirty-nine kilometres, though most run under five. They cut across lower Eocene to Oligocene extension fractures caused by local overpressure in the underlying oil shale — the same mechanism that formed the Utah deposits.
Iran and Utah: an honest comparison
Two countries produce gilsonite in commercial quantity, and a buyer should know the difference rather than be told only one side of it.
| Utah, United States | Iran | |
|---|---|---|
| Deposit size | The world’s largest | The largest outside the United States |
| Name | Gilsonite® is a registered trademark of American Gilsonite Company; the mineral name is uintaite | Sold as gilsonite, natural bitumen or natural asphalt; the same mineral class |
| Mining | Underground shafts and drifts, hand-worked with chipping hammers | Vein mining in the western provinces |
| Lead time to most markets | Longer, with US export logistics | Shorter to the Middle East, Asia and Africa |
| Typical cost delivered | Higher | Lower for non-American destinations |
For a buyer in North America, Utah material is the natural choice. For most of the rest of the world the freight and lead time make Iranian material the practical one, provided the mine of origin is specified. Background on the American deposits is on our Utah gilsonite mine page.
We describe our material as gilsonite, natural bitumen or natural asphalt according to what the buyer’s specification calls it. Gilsonite® as a registered trademark refers to American Gilsonite Company’s product, and we do not represent our material as theirs.
Forms and grades supplied
The same ore is supplied in several physical forms, and the right one depends on how it will be dosed rather than on what it costs.
| Form | Typical use | Why this form |
|---|---|---|
| Powder, various mesh | Drilling fluid, asphalt modification, ink | Disperses and dissolves quickly; mesh chosen to suit the mixing equipment |
| Micronised | Ink, paint, fine coatings | Where particle size governs gloss and dispersion |
| Granulated | Hot mix asphalt plants | Flows through dosing equipment without bridging or dusting |
| Lump | Buyers who grind on site | Lowest cost per tonne where milling capacity exists |
| Ore and rock | Processors and resellers | Raw material for their own grading and packing |
Composition: volatiles and residue
Gilsonite contains two kinds of carbon structure, a straight chain and a ring. Heating separates them: the ring fraction vaporises as volatiles and the straight fraction remains as residue, sometimes called the carbon or carbon black. Typical Iranian material runs over 60 per cent volatiles and under 40 per cent residue, with residue usually in the 36 to 38 per cent range. Volatile content is normally reported as loss on ignition.
The residue is exported in its own right as a carbon product. The volatile fraction, once condensed, can serve as a refinery or petrochemical feedstock, though it needs refining to remove sulphur before use as fuel.
Gilsonite is a mined mineral, so its analysis varies between veins and between batches in a way a manufactured product does not. Read the batch certificate rather than the data sheet, and specify the parameters your process is actually sensitive to.
What Iranian gilsonite is used for
Gilsonite appears in more than 160 products. These are the markets that take volume.
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Drilling fluid
Fluid loss control, filtrate control and hole stabilisation in HTHP and HTLP wells. It softens at downhole temperature, plugs micro-fractures and smears the wellbore into a tough filter cake.
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Shale inhibition
Reacts with reactive shale to prevent sloughing and swelling, which is the failure mode that costs most rig time in water-based systems.
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Oil well cement
Lost circulation material and slurry density reducer in specialty cementing fluids, working on the same plugging and binding properties.
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Asphalt modification
Raises resistance to rutting and permanent deformation in hot mix, and to thermal cracking in cold climates.
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Printing ink
Wets and disperses carbon black pigment and binds it to newsprint so it does not rub off. The historic core market.
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Paint and coatings
Primer, mastic, varnish and enamel formulations, where it adds durability and acid and alkali resistance.
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Foundry sand
Added to moulding sand for a smoother cast finish and easier release. This is where the lower-grade Lorestan material belongs.
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Roof and building coatings
Roof coating, building product coating, road seal coat and crack sealer compounds.
Using gilsonite in asphalt
This is the application where dosing and procedure decide the result, so it is worth setting out properly.
Where it earns its keep
Gilsonite is used on the parts of a road that fail first: junctions, bus stops, signal approaches and truck corridors, where vehicles stand still under load and the surface shoves and ruts rather than wearing evenly. It raises resistance to permanent deformation and to fatigue, and it also reduces cracking at low temperature — which is unusual, because most hardening additives buy heat resistance at the cost of cold flexibility.
Dosing and mixing
| Parameter | Figure | Notes |
|---|---|---|
| Performance dosage | 13–14% of binder | Where a measurable performance gain is the objective |
| Typical substitution | 5–10% | The common working range in production |
| Minimum mixing temperature | 170–175 °C | Below this the mixing time extends sharply |
| Mixing time at 5–10% | 2–4 hours after addition | With recirculation through the piping |
| Master batch above 10% | Overnight recirculation | Preferred for concentrated pre-blends |
Add the gilsonite slowly at the vortex rather than dumping it, and arrange to recirculate the hot bitumen through the piping while it goes in. Material with a softening point near 150 °C blends most easily at these temperatures.
The practical consequence. In cold-weather paving, gilsonite lets you work from ordinary 50/70 penetration bitumen instead of sourcing a special grade. That is usually the whole commercial case for using it: the modifier costs less than the premium binder it replaces, and it is available where the premium binder is not.
Gilsonite with reactive oil
Asphalt cement can be toughened with gilsonite and thinned with a reactive oil — an oil high in unsaturated fatty acids. The oil keeps viscosity low enough to lay, then cures after application, so the mat gains its rut resistance on the road rather than in the tank. It is a route worth discussing where application viscosity is the constraint.
Physical and chemical character
Gilsonite is a black solid of fairly bright lustre. Freshly broken surfaces look like obsidian; weathered surfaces look like coal, which is how the first Utah miners came to mistake it for coal in 1868. Rubbed on paper or white porcelain it leaves a brown streak, where inferior asphalts leave a black one — a field test that still works.
| Property | Character |
|---|---|
| Mineral class | Asphaltite; mineralogical name uintaite |
| Appearance | Black solid, bright lustre when fresh |
| Streak | Brown |
| Softening / fusion range | 130–210 °C depending on grade |
| Hydrocarbon purity, Kermanshah and Ilam | Up to 98% |
| Volatiles | Over 60% typical |
| Residue | 36–38% typical |
| Solubility | Soluble in aromatic and chlorinated organic solvents; measured against ASTM D2042 in trichloroethylene |
| Compatibility | Coating materials, petroleum resin and oil, pitch and bitumen blends, vegetable oil |
| Chemical resistance | High resistance to acid and alkali |
The ore is composed mainly of nitrogen, sulphur and oxygen compounds with subordinate saturated and aromatic hydrocarbons. For the wider mineral family and how gilsonite sits within it, see natural bitumen and gilsonite bitumen.
Frequently asked questions about Iran gilsonite
Where is gilsonite mined in Iran?
The principal deposits are in the west of the country: Gilan-e Gharb and Qasr-e Shirin in Kermanshah province, and in Ilam province toward the Iraqi border. A further deposit at Kuhdasht in Lorestan has a much lower hydrocarbon content and is used only for foundry work. The Kermanshah and Ilam material is the first-quality grade, with purity up to 98 per cent.
Is Iran the only country with gilsonite mines?
No. Two countries produce it in commercial quantity. The largest deposits in the world are in the Uinta Basin of Utah in the United States. Iran holds the largest deposits outside the United States and is the practical source of supply for most markets outside North America, on freight and lead time.
Does the mine of origin change the material?
Substantially. Kermanshah and Ilam ore carries a high hydrocarbon content and performs in drilling fluid and asphalt modification. Kuhdasht ore in Lorestan is markedly lower and is suitable only as a foundry sand additive. Both are sold as Iranian gilsonite, so name the mine region in the contract rather than relying on the grade name alone.
What is the difference between gilsonite, natural bitumen and natural asphalt?
In commercial use they describe the same mineral, an asphaltite whose formal mineralogical name is uintaite. Gilsonite® is also a registered trademark of American Gilsonite Company and refers to their Utah product. We supply the mineral and describe it by whichever name your specification uses.
How much gilsonite is added to asphalt?
Production substitution typically runs 5 to 10 per cent of the binder; 13 to 14 per cent is where a clear performance gain shows. Mix at a minimum of 170 to 175 degrees Celsius, adding slowly at the vortex with the hot bitumen recirculating, and allow 2 to 4 hours of mixing after addition. Master batches above 10 per cent are better recirculated overnight.
What does gilsonite do in drilling fluid?
It controls fluid loss and filtrate, and stabilises the hole. At downhole temperature it partially softens, plugs micro-fractures in the formation and smears the wellbore wall into a tough, tight filter cake. It also inhibits reactive shale, preventing the sloughing and swelling that cause stuck pipe. It works in oil-based, water-based and synthetic systems.
What forms and mesh sizes are available?
Powder in a range of mesh sizes, micronised powder, granulated, lump, and raw ore or rock. Powder and micronised grades suit drilling fluid, ink and paint; granulated suits hot mix asphalt dosing equipment; lump suits buyers who grind on site. Tell us the dosing equipment and we will say which form fits.
What is the volatile and residue content?
Typically over 60 per cent volatiles and under 40 per cent residue, with residue usually between 36 and 38 per cent. Volatile content is normally reported on the certificate as loss on ignition. The residue fraction is itself exported as a carbon product.
At what temperature does gilsonite soften?
Between about 130 and 210 degrees Celsius depending on the grade. For asphalt blending, material with a softening point near 150 degrees blends most readily at normal plant temperatures.
Can you supply against our own specification?
Yes. Send the specification rather than a grade name, including the mine region if your process is sensitive to it, and we will confirm what we can meet before you commit. Every shipment carries a batch certificate of analysis.
Related pages
Technical reference: gilsonite specification, natural bitumen and gilsonite bitumen. Origins: the Utah gilsonite mine.
Applications: drilling fluid, oil well cementing, asphalt, ink, paint and construction. The wider oilfield range is on our oil and gas and drilling fluid products pages.
Request a quotation for Iran gilsonite
Send us the quantity, the form and mesh you need, the application, and the discharge port. If your specification is sensitive to the mine of origin, say so and we will confirm the region before the cargo is allocated. Batch certificate of analysis with every shipment, third-party inspection accepted at loading.
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