Gilsonite is a naturally occurring solid hydrocarbon — a high-purity asphaltite rich in asphaltenes and nitrogen compounds, registered under CAS number 12002-43-6. It is glossy black, brittle, low in sulfur and ash, and soluble in aromatic and aliphatic solvents as well as petroleum asphalt. Buyers also encounter it as natural bitumen, mineral bitumen, natural asphalt, asphaltum, uintaite and hard asphalt. Those names are not interchangeable in every context, and this page explains where the differences matter.
What is gilsonite?
Some asphalts are made by nature rather than by refining. Over long periods, crude oil trapped in the earth loses its volatile fractions under pressure and atmospheric action, and what remains is a solid black hydrocarbon. That material is natural bitumen, and it outlasts refinery asphalt in service.
It occurs in two forms. Some is found as surface accumulations — the asphalt lakes, of which Trinidad’s Pitch Lake is the best known. The rest is mined from underground veins, and that material is what the trade calls mineral bitumen or gilsonite.
Chemically it is a high-purity solid hydrocarbon rich in asphaltenes and nitrogen compounds. It appears similar to hard coal or asphalt but behaves differently: it is thermoplastic, so it melts rather than burns, and it is soluble in organic solvents. It is classified as an asphaltite.
Because of its unusual compatibility with petroleum products, gilsonite is frequently used to harden softer ones — which is the basis of most of its industrial applications.
The names: gilsonite, uintaite, natural bitumen, asphaltite
Four names circulate for what buyers often treat as one material, and the distinctions matter when you are reading a specification or a tender document.
| Term | What it strictly means | How it is used in trade |
|---|---|---|
| Asphaltite | The mineralogical class — solid hydrocarbons found in oil-bearing sedimentary basins, typically as veins | The correct technical umbrella term |
| Uintaite / uintahite | The scientific mineral name for this specific asphaltite | Used in academic and regulatory documents; rarely in commerce |
| Gilsonite | Named after Samuel H. Gilson; adopted and trademarked by an early mining company | The dominant commercial name worldwide, used generically across the industry |
| Natural bitumen / natural asphalt | Broader category including asphaltites and asphalt lake material | Common in export documentation and customs classification |
Why the naming matters commercially. Gilson was not the original discoverer, but his promotional efforts attached the material to his name, and people in the region began referring to it as gilsonite rather than by its scientific name, uintaite. The name then solidified in common usage when an early mining company adopted and trademarked it. Today the term is used generically across the industry for asphaltite of this type, while remaining a registered trademark in some jurisdictions for material from specific deposits. If your tender specifies a property — softening point, ash, solubility — that is what determines fitness. If it specifies only a name, ask which property is actually required.
Composition and structure
Gilsonite is composed predominantly of carbon and hydrogen, with smaller amounts of nitrogen, sulfur, oxygen and trace metals. The high carbon and nitrogen content is what produces its distinctive properties.
| Element or property | Typical value | Significance |
|---|---|---|
| Carbon | Approximately 85% | The basis of its hydrocarbon character and compatibility with petroleum products |
| Hydrogen | Approximately 10% | Low hydrogen-to-carbon ratio reflects the high aromaticity |
| Nitrogen, sulfur, oxygen, metals | The balance | Nitrogen content is unusually high for a bituminous material and contributes to its binding behaviour |
| Average molecular weight | Approximately 3,000 | Higher than refinery asphalt products and synthetic resins; behaves as a quasi-polymer |
| Ash content | Low; graded by application | The governing specification for drilling fluid and ink applications |
| Sulfur | Low | Matters in foundry and some chemical applications |
Within the structure, aromatic compounds including pyrrole, pyridine and furan rings appear alongside chain aliphatic groups and amide groups. The full structural picture is built up using FT-IR, NMR, TGA, VPO, HPLC, GC-MS and CHNOS analysis. Our molecular structure and chemical characterization pages cover the analytical detail.
Solubility
Gilsonite dissolves in organic solvents including carbon disulfide, toluene and tetrachloroethylene, and in petroleum asphalt. It is insoluble in water and in alcohol solvents.
That solubility profile is the basis of most of its uses: it allows the material to disperse into oil-based systems and function chemically rather than merely sit in them as a filler. It is also why water based drilling muds require a sulfonated form, since an untreated hydrocarbon will not disperse in water.
How gilsonite occurs
Gilsonite occurs in disseminated blebs and in dikes or veins, sills and fracture fillings, often in association with oil shale or bituminous deposits such as tar sands.
The veins run nearly parallel to one another and may extend many kilometres in length. A vein typically shows at the surface as a thin outcrop and widens with depth. Vein width generally ranges from 0.5 to 2 metres, occasionally reaching 5.8 metres.
On a weathered surface it has a dull, black, coal-like appearance. Break it fresh and the conchoidal to hackly fracture surface is shiny and black, resembling obsidian. In the deepest parts of some veins, a small proportion is semisolid or present as a liquid ooze — gilsonite solidifies as its organic compounds oxidise and it loses hydrogen.
Historical grading by appearance
Industry once defined three major subdivisions based on appearance and fusing temperature.
| Variety | Appearance | Fusing temperature | Where it occurs in the vein |
|---|---|---|---|
| Selects | Very shiny | 149–168 °C | Vein centres |
| Seconds | Somewhat duller | 152–183 °C | Vein margins, sometimes with a columnar jointed pencillated texture |
| Jet | Brilliantly shiny, bluish black | 199–230 °C | Rare; historically found in one vein only |
Pencillated texture forms at right angles to the vein walls and penetrates about 15 cm into the ore. Gilsonite also shows a flaky or scaly texture in some localities. Historical classification follows Abraham (1960).
Modern practice has moved on. Gilsonite is now classified by fusing temperature into five ranges, which are used in different applications and priced differently. Material from different veins, or from different parts of the same vein, is blended to achieve a specific fusing temperature range. That is why the specification matters more than the deposit name when you order.
Where gilsonite is found
Natural bitumen deposits occur across many oil-bearing basins. The largest are in North America, with significant reserves also recorded in Canada, Iraq, Russia, Venezuela, China, Australia, Mexico and the Philippines.
World natural bitumen reserves are estimated at roughly 100 million tonnes, with around 65% of that total in North America. Deposits are generally found in oil-rich regions.
Asphaltite deposits specifically are numerous — dozens have been identified and many have been mined — but commercially viable ones are less common, because the deposit must be large enough, pure enough and accessible enough to work economically.
Mining
Because the mining face is narrow, gilsonite is extracted today much as it was fifty or a hundred years ago: hand-mined in underground shafts. The principal difference is that modern miners use pneumatic chipping hammers and mechanical hoists rather than hand tools.
From the mine, material is separated by temperature grade, dried, screened, sized to customer specification and subjected to quality control before shipment. See our gilsonite rock and natural bitumen pages for more on the raw material.
What gilsonite is used for
Gilsonite appears in more than 160 industrial products. Some use it in crude form — as pipeline insulation, particularly for hot lines, as waterproofing and undercoating for wood and metal, and in paving and roofing much as crude asphalt is used. More often it is blended into refinery asphalt and petroleum products to obtain specific characteristics.
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Drilling fluids
Fluid loss control, lost circulation prevention, shale stabilisation and wellbore strengthening in oil based and water based systems.
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Oil well cementing
Lightweight cement additive for lost circulation control and slurry density reduction.
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Asphalt modification
Raises softening point and rut resistance in hot mix, producing substantially more stable paving mixes.
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Printing inks
Wets and disperses carbon black pigment and binds it to newsprint so it does not rub off.
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Paints and coatings
Black pigment and binder for protective and anti-corrosion coatings, and for wood stains.
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Foundry
Sand additive producing a smoother cast finish and easier unmoulding.
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Construction and waterproofing
Adhesive and waterproofing agent in roofing felt manufacture, sealants and building papers.
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Chemical products
Feedstock and modifier across an extensive range of industrial formulations.
Health and safety
Gilsonite is a very pure resinous rock made of a combination of hydrocarbons. It is non-hazardous and non-toxic, and no case of toxicity has been reported.
| Property | Gilsonite | Coal and fly ash |
|---|---|---|
| Toxicity | Non-toxic | Toxicity concerns documented |
| Carcinogenicity | Non-carcinogenic | Concerns documented |
| Mutagenicity | Non-mutagenic | Concerns documented |
| Handling | Standard PPE, no extreme measures | Dust control required |
| Deepwater discharge | Passes Gulf of Mexico EPA requirements for deepwater operations | Generally restricted |
The deepwater discharge position is documented in an AADE paper — see our deepwater drilling page, which hosts the study in full. Handling and disposal information is in the gilsonite MSDS.
Frequently asked questions about gilsonite
What is gilsonite?
A naturally occurring solid hydrocarbon — a high-purity asphaltite rich in asphaltenes and nitrogen compounds, CAS number 12002-43-6. It forms when crude oil trapped underground loses its volatile fractions over long periods, leaving a solid black material. It is glossy black and brittle, low in sulfur and ash, soluble in organic solvents and in petroleum asphalt, and thermoplastic — it melts rather than burns.
What is the difference between gilsonite, uintaite and natural bitumen?
Uintaite is the scientific mineral name. Gilsonite is the commercial name, taken from Samuel H. Gilson and later adopted and trademarked by an early mining company; it is now used generically across the industry. Asphaltite is the mineralogical class the material belongs to. Natural bitumen and natural asphalt are broader terms covering both mined asphaltites and asphalt lake material. When reading a specification, go by the stated properties rather than the name.
What is gilsonite made of?
Predominantly carbon, around 85%, and hydrogen, around 10%, with smaller amounts of nitrogen, sulfur, oxygen and trace metals. The unusually high nitrogen content contributes to its binding behaviour. Average molecular weight is approximately 3,000, higher than refinery asphalt products and synthetic resins, and it behaves as a quasi-polymer compound.
Is gilsonite the same as coal?
No. It was once thought to be a type of coal because weathered surfaces look similar, but its chemical properties are significantly different. The decisive difference is that gilsonite is thermoplastic — it melts rather than burns — and it dissolves in organic solvents, which coal does not.
What is gilsonite soluble in?
Organic solvents including carbon disulfide, toluene and tetrachloroethylene, plus aromatic and aliphatic solvents generally, and petroleum asphalt. It is insoluble in water and in alcohol solvents. That profile is why water based drilling muds require a sulfonated form, since an untreated hydrocarbon will not disperse in water.
How is gilsonite graded?
Modern practice classifies it by fusing temperature into five ranges, which suit different applications and carry different prices. Material from different veins, or different parts of the same vein, is blended to achieve a specified range. Historically the industry used three appearance-based grades — selects, seconds and jet — with fusing temperatures from 149 to 230 °C.
How is gilsonite mined?
Hand-mined in underground shafts, because the vein is narrow. The method has changed little in a century; the main difference is that modern miners use pneumatic chipping hammers and mechanical hoists. Veins run 0.5 to 2 metres wide, occasionally up to 5.8 metres, and may extend many kilometres in length.
What is gilsonite used for?
More than 160 industrial products. The main applications are drilling fluids and oil well cementing, asphalt modification for paving, printing inks, paints and coatings, foundry sand additives, roofing felt and waterproofing, and a wide range of chemical formulations. It is used both in crude form and blended into refinery asphalt and petroleum products.
Is gilsonite toxic?
No. It is non-hazardous and non-toxic, and no case of toxicity has been reported. It is also non-carcinogenic and non-mutagenic, unlike coal or fly ash, and requires only standard PPE for handling. It passes Gulf of Mexico EPA discharge requirements for deepwater operations.
Why is gilsonite used to harden petroleum products?
Because of its unusual compatibility with them. It dissolves into petroleum asphalt rather than sitting in it as a filler, and its high molecular weight and asphaltene content raise the hardness and softening point of the blend. That is the mechanism behind its use in asphalt modification and in hardening softer petroleum products generally.
What forms and particle sizes are available?
Lump, granular and micronized powder, with mesh sizes of 30–40, 100, 200, 300 and custom cuts. Ash content, softening point and particle size distribution are adjusted to the application — low-ash grades under 5% ash are available where ash content governs, as in drilling fluids and inks.
What should be on the certificate of analysis?
Softening point, ash content, moisture, volatile matter, solubility, particle size distribution and the lot number with production date. Which of those governs depends on the application: ash for drilling fluids and inks, softening point for asphalt modification and cementing, particle size for foundry and powder blending. Ask for the measured batch values, not a typical-values sheet.
Related pages
Properties and analysis: gilsonite properties, specification, analysis, molecular structure, metal content, chemical characterization and technical advantages.
Related materials: natural bitumen, natural asphalt, gilsonite bitumen, gilsonite rock, bitumen powder, tar sands, coal tar and bituminous coal.
Applications: all applications, drilling fluids, cementing, asphalt, ink, paint, foundry, construction and chemical products.
Commercial: price, MSDS, HS code and history.
Tell us the application, not just the name
Send us what the material has to do — the industry, the formulation, the property that governs — and we will confirm which grade fits, state the measured softening point and ash on the batch certificate of analysis, and accept third-party inspection at loading. We separate by temperature grade, dry, screen and size to customer specification, with quality control before shipment to over 80 countries.
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