Natural Asphalt and Gilsonite: What They Are and What They Are Not

The words are difficult before anyone is being dishonest. Asphalt and bitumen already mean different things on different continents, a problem set out in full on bitumen versus asphalt terminology. Natural asphalt then adds a second layer, because it is not a product. It is a family name covering several unrelated mined materials whose only shared feature is that a hydrocarbon reached or approached the surface of the earth and lost its light ends there, rather than being separated in a refinery column.

Refined paving bitumen is manufactured. Its consistency is set by the process, it is certified against a published grade specification, and one drum is deliberately made to behave like the next. Natural asphalt is mined. Its composition is a property of the deposit, it varies from one working face to another, and there is no product standard anywhere that tells a producer what a tonne of it must contain. That single difference — manufactured to a specification against dug out of the ground — is the origin of every commercial problem on this page.

The terms, as the road materials vocabulary uses them

ASTM D8, the terminology standard for materials for roads and pavements, is the document that fixes these words for technical purposes, and it is worth quoting the distinctions rather than paraphrasing them loosely:

• Natural asphalt (also native asphalt) — asphalt occurring in nature, formed from petroleum by natural processes of loss of volatile matter and oxidation. It is the umbrella term, and on its own it tells a buyer almost nothing.
• Lake asphalt — a natural asphalt occurring as a surface accumulation, typically a mixture of bitumen, finely divided mineral matter, water and gas. Trinidad and the Bermudez deposit in Venezuela are the classic examples.
• Rock asphalt — a naturally occurring sandstone or limestone impregnated with bitumen. The defining feature is that the material is rock first: the bitumen is the minority phase.
• Asphaltite — a naturally occurring solid hydrocarbon, hard and largely soluble in carbon disulfide, distinguished from the softer native asphalts by its hardness and its high softening point. The three named members of the group are uintaite (traded as gilsonite), glance pitch (also called manjak) and grahamite, ranked roughly in that order by increasing fixed carbon and decreasing fusibility.
• Asphaltic pyrobitumens — materials such as wurtzilite and albertite that resemble the asphaltites but are largely insoluble in carbon disulfide. They are geological neighbours of gilsonite and industrially useless as binder-related products, which is precisely why the solubility test matters when a mined black solid is offered to you.
• Oil sands or tar sands — sand or porous rock saturated with a very viscous natural bitumen. These are a hydrocarbon feedstock, processed and upgraded like a crude, and they do not reach the market as a natural asphalt product.

What all of them have in common

Four things, and all four are commercial rather than chemical:

• No product standard sets their composition. There is no ASTM D946 or EN 12591 for gilsonite, for lake asphalt, for rock asphalt or for asbuton. There are excellent test methods for measuring what is in them, and this page names them throughout, but a test method sets no limits. Everything you are told about composition comes from a producer data sheet or a lot certificate, and it has to be verified rather than assumed.
• They vary. A vein narrows, a bench changes, a working face moves into a dirtier zone, and the ash content moves with it. Consistency between lots is a real risk that a buyer carries and that no grade name protects against.
• The hydrocarbon in them is heavily aged. These materials have spent geological time losing volatiles and oxidising. They are high in asphaltenes, hard, and generally brittle at low temperature. That is what makes gilsonite a useful hardener, and it is also why none of them behaves like a fresh refined binder.
• Most of them carry mineral matter that stays. Refining Trinidad lake asphalt removes water and debris, not mineral. Crushing rock asphalt does not separate the bitumen from the stone. Where the mineral is present it is part of what you buy, part of what you ship, and part of what has to be designed into the mix.

Why the confusion is commercially dangerous

Natural asphalt came first. Mastic asphalt technology grew out of European bituminous limestone in the nineteenth century, and asphalt lake material was being shipped for road and waterproofing work long before penetration grading existed. Refined bitumen displaced it for road paving for one reason: a refinery can make the same thing again next month, and a deposit cannot. That history is why natural asphalt still sounds to many buyers like the original and therefore superior article, and why the phrase natural bitumen 60/70 circulates in the trade at all.

There is no such grade. Penetration grades are defined for refined petroleum bitumen by ASTM D946 and EN 12591, and both of those specifications contain a solubility line that a mineral-bearing natural asphalt cannot pass. The rest of this page covers each material properly and separately, and then returns to that point, because it is the one that decides whether an offer in front of you is worth reading.

What it is

Uintaite is a naturally occurring solid hydrocarbon of the asphaltite group. It formed where petroleum migrated into open joints and fractures in the rock and then lost its light ends and oxidised in place over geological time. What remains is a hard, brittle, glassy black solid, very high in asphaltenes and notably high in nitrogen compared with most petroleum bitumens, largely soluble in carbon disulfide and in the chlorinated and brominated solvents used for solubility testing.

In the hand it is unmistakable. It is jet black with a bright, almost resinous lustre, it breaks with a conchoidal fracture like glass or obsidian, it leaves a brown streak, and it is extremely friable — it crumbles to a fine dust with very little effort. That friability is a processing advantage, because grinding it is easy, and a serious safety liability, for the reason set out at the end of this section.

How it is mined

Gilsonite does not occur in beds. It occurs in near-vertical veins — dikes of solid hydrocarbon filling fractures, running broadly northwest to southeast across the basin, traceable at surface for long distances and continuing to considerable depth. Vein widths are reported in the mining literature as running from a few centimetres to a few metres, which is the governing fact of the whole operation: the ore body is narrow, so the mining method has to be narrow too.

• Underground mining along the vein. Shafts are sunk on the vein and the material is worked from within it, so that the mine follows a thin vertical sheet rather than opening a stope. Historically the work was done by hand with picks and pneumatic chipping tools; mechanical and hydraulic methods and vacuum recovery of the broken material to surface have since been introduced.
• Surface working where a vein outcrops. Where the vein reaches or nears the surface it can be trenched from above for the upper section.
• Wall rock is the contamination source. The purity of a lot is decided by how much of the enclosing rock comes with the hydrocarbon. A clean, well-defined vein worked carefully yields a low-ash material; a wider, dirtier or more broken section yields a higher-ash one. This is why ash content is a grading parameter rather than a fixed property, and why it has to be certified lot by lot.

How it is graded and sold

Gilsonite is offered against three parameters, and it is worth being precise about their status: none of them is a standard grade designation. They are supplier grade designations, and two suppliers using the same words may not mean the same material.

• Softening point band. Commercial grades span a wide range; supplier grade literature commonly describes bands running from around 120 °C to above 200 °C. Those are supplier-published typical bands and not limits set by any standard, so treat them as a description of what is offered rather than as a specification. The band is the primary selling parameter and it is what most non-road users are actually buying.
• Ash content. Select grades are offered low in ash; grades cut from wider or dirtier vein sections carry more. This is the number that decides whether a material is a hydrocarbon additive or a hydrocarbon-and-rock additive.
• Particle size. Lump, granular, ground and micronised powder, sized by sieve. For a binder modifier the fineness governs how quickly and how completely it goes into solution; for drilling and foundry work the size distribution is functional in its own right.

Handling: the hazard that is specific to this material

Finely divided gilsonite is a combustible dust. That is not a general caution about housekeeping; it is the reason this material is handled differently from bitumen in every plant that uses it. A friable hydrocarbon solid that grinds easily produces exactly the particle size range that forms an explosible atmosphere in a silo, a bag filter, a screw conveyor or a bucket elevator. Handling has to be designed to the combustible dust rules that apply where you are — in the United States these were consolidated by the National Fire Protection Association into NFPA 660, superseding the earlier NFPA 652 and NFPA 654 documents, and in Europe the ATEX framework governs the same problem. Bond and earth transfer equipment, control ignition sources, contain and extract dust at every transfer point, and do not treat a bag of ground gilsonite as though it were a bag of filler.

Two lesser handling points matter in practice. The material softens and cakes in warm storage, so bagged product left in a hot container or an unshaded stack can arrive as a consolidated block rather than a free-flowing powder. And it stains comprehensively: it marks concrete, clothing and equipment, and the marks are not readily removed.

The confusion that catches buyers out

Gilsonite is routinely confused with two other black solids, and the confusion runs in both directions. The first is oxidised (blown) bitumen, which is manufactured by blowing air through a bitumen feedstock and which also has a high softening point and a very low penetration. On a certificate showing only those two properties the materials look alike. They are not: one is a mined mineral product and the other is a refinery product, they are classified differently for customs, and they behave differently in a blend. The second is the rest of the asphaltite group — glance pitch and grahamite — which are genuinely natural, genuinely mined and genuinely not uintaite. In both cases the separating evidence is a full certificate rather than a description: ash by ASTM D482, solubility by ASTM D2042, softening point by the right method for the range, and volatile matter and fixed carbon on a proximate analysis.

What it does

Charged into hot bitumen with adequate temperature and agitation, gilsonite goes into solution in the binder. Being itself an extremely asphaltene-rich hydrocarbon, it shifts the whole binder toward the asphaltene end: the material gets harder, the penetration falls, the ring-and-ball softening point rises, and the complex modulus at high service temperature rises with it. In performance grading terms the high-temperature grade improves, which is the effect users are buying.

The dose is small. Published research and supplier guidance most often work in the region of 3 to 8 percent by mass of binder, with higher additions reported where a very hard binder is the objective. Those figures are typical practice reported in the literature and in supplier guidance, not a requirement of any standard — no standard specifies a gilsonite dose, for the same reason no standard specifies an anti-stripping dose: the right addition depends on the base binder, the target and the mix, and it has to be established by testing the actual materials.

How it is blended

• Temperature and shear. Blending is normally done in the region of 160 to 180 °C with high-shear or vigorous mechanical mixing, held long enough for the solid to dissolve rather than merely disperse. This is common practice rather than a specified procedure; the binding figures are the ones the modifier supplier states for the grade and particle size you have bought.
• Undissolved gilsonite is filler. Particles that have not gone into solution do not modify anything. They sit in the binder as inert solids, they will show up as insoluble matter on a solubility test, and they change the mix volumetrics without delivering the stiffening that was paid for. Fineness and mixing time are therefore not incidental.
• Storage after blending. Because the relative density of gilsonite is close to that of bitumen, a properly dissolved blend is less prone to the gross separation that some polymer systems show. That is not a licence to leave a blend standing unagitated indefinitely; verify separation behaviour on the actual blend rather than assuming it.
• Dust at the charging point. Ground gilsonite is being introduced into a hot tank. The combustible dust precautions above apply at exactly that point, together with the ordinary hot bitumen rules: never introduce anything containing water into a hot tank, confirm ullage, and use a closed charging arrangement rather than an open hatch. The thermal hazard at that point is ordinary but real: a solid going into binder held in the region of 160 to 180 °C can cause the surface to lift and spit, so full face protection, heat-resistant gauntlets and covering clothing are worn at the hatch, nobody stands in the vent path, and the charging rate is kept slow enough that the tank does not surge.

The trade-off nobody puts on the data sheet

Stiffening a binder is a trade-off rather than a straight gain, and the test suite makes the other half of it visible if you run the whole suite instead of the flattering half. The methods that show it are the standard performance grading ones: ASTM D7175 / AASHTO T 315 for the dynamic shear rheometer, ASTM D2872 / AASHTO T 240 for the rolling thin film oven, ASTM D6521 / AASHTO R 28 for the pressure ageing vessel, and ASTM D6648 / AASHTO T 313 for the bending beam rheometer, all assembled into a grade under ASTM D6373 / AASHTO M 320.

• The high-temperature end improves. Higher stiffness at service temperature means better resistance to permanent deformation, which is the case for using the material at all.
• The low-temperature end generally suffers. A stiffer, more asphaltene-rich binder tends toward a higher creep stiffness and a lower m-value on the bending beam rheometer after ageing. In grading terms the low-temperature limit moves the wrong way, so the useful temperature interval does not widen as much as the high-temperature gain on its own suggests. Where thermal cracking governs, this is the decisive number and it has to be measured, not assumed.
• Ageing. The material is already heavily oxidised by geological time. Run the RTFO and PAV residues rather than judging the blend on original binder properties.

Gilsonite is not a polymer, and the tests say so

This is the most commonly mis-sold aspect of the material. Gilsonite hardens a binder; it does not make it elastic. Under ASTM D7405 / AASHTO T 350, the multiple stress creep recovery test, a gilsonite-modified binder typically shows an improved non-recoverable creep compliance — the resistance to permanent deformation genuinely gets better — while the percent recovery stays low, because there is no elastomeric network to pull the material back. The same conclusion arrives from ASTM D6084, elastic recovery by ductilometer, which is why that test appears in polymer modified binder specifications and is not satisfied by hardening alone.

The practical consequence is that gilsonite modification and polymer modification are not alternatives for the same job. Where a specification asks for elastic recovery, or for a percent recovery limit at a given stress level, a hardened binder will not meet it however high its softening point goes. See polymer modified bitumen for what an elastomeric system actually delivers, and the performance grading guide for how the two show up differently across the grade.

The honest alternatives

If the objective is simply a harder binder, gilsonite modification is one route among several, and it is worth comparing it with the routes that are manufactured to a published specification:

• A hard paving grade. Bitumen 20/30 and the neighbouring hard grades are refined products certified against ASTM D946 or EN 12591. They arrive with a specification, a grade name and a certificate, and they need no blending step, no dust handling and no verification that the modifier dissolved.
• Oxidised bitumen, where the application is industrial rather than paving and a high softening point with low temperature susceptibility is what is wanted.
• Polymer modification, where elasticity, fatigue resistance and low-temperature performance matter and not merely stiffness.

The abuse to watch for

Because gilsonite hardens a binder quickly and with very little equipment, it can be used to bring an off-specification soft cargo onto a penetration figure. The blended material may then report a penetration and a softening point inside the grade limits while being a different material in every other respect — poorer ductility, a worse low-temperature grade, and, if an ash-bearing gilsonite grade was used, a solubility result that fails the paving grade specification outright. Nothing about this appears on a certificate that reports only penetration and softening point. It is one of the specific patterns covered on bitumen fraud prevention, and the defence is the same as it is there: a full certificate against the full specification, on the delivered lot, with independent sampling.

Trinidad Lake Asphalt

The Pitch Lake at La Brea in Trinidad is a surface accumulation of natural asphalt whose published dimensions are commonly given as roughly forty hectares, about a hundred acres, and something in the order of seventy-five metres deep at its centre. Those are the figures customarily reported for the deposit, not measurements this page can verify, and nothing commercial should rest on them. It is not a static pool. Material wells up from below and the deposit slowly refills behind the working face, which is why it has been dug continuously for well over a century.

How it is won. The raw material is dug from the surface of the lake with excavating plant and carried away for processing. Processing is a refining step in the narrow sense: the raw lake asphalt is heated in kettles to drive off its water and to allow coarse vegetable debris and tramp material to be screened out, leaving the refined product traditionally called epuré. Understand precisely what that step does and does not do. It removes water and rubbish. It does not remove the mineral matter, which is present as an extremely fine, colloidally dispersed solid throughout the bitumen and is an inseparable part of the product.

What it contains. The composition is a property of the deposit rather than a formulation, and the correct way to describe it is in kind: on the figures customarily published for the deposit, raw lake asphalt is roughly half bitumen by mass, with a large fraction of very fine mineral matter and a significant water content, plus occluded gas. No standard sets any of those proportions. Refining removes the water, so the refined product is bitumen and mineral in roughly the same proportion to each other as before, concentrated by the loss of the water. Producer data sheets publish typical figures for the refined material, commonly putting the soluble bitumen a little above half by mass and the mineral matter at roughly a third. Those are producer-published typical values, not a standard requirement, and the figures that matter commercially are the ones on the certificate for the lot you are actually buying: bitumen content by ASTM D4 or solubility by ASTM D2042, ash by ASTM D482 and water by ASTM D95.

How it behaves. Refined lake asphalt is very hard. Penetration at 25 °C by ASTM D5 is typically reported in low single figures, and the ring-and-ball softening point by ASTM D36 well above the paving grade range; both are producer-reported typical values rather than limits set by any specification, and both have to be read off the lot certificate. The mineral is so fine that it behaves as an integral part of the binder phase — a natural filled mastic rather than a binder with stones in it — and that is the property that makes the material technically interesting rather than merely heavy.

What it is used for. Two things, both of them established over a long period. It is blended with paving bitumen as a modifier, raising stiffness and improving deformation resistance in surfacing mixtures; the blend proportion is a specification decision and the published ratios vary widely by country and by application, so no single ratio should be quoted as standard. And it is used in mastic asphalt and specialist surfacing — bridge deck surfacing, heavy-duty and industrial paving, and mastic work covered by documents such as EN 13108-6 and the national mastic asphalt standards that preceded it. In mastic asphalt the mineral fraction is not a nuisance at all; the recipe is built around a high filler content and the lake material contributes to it deliberately.

The mistake to avoid. Substituting refined lake asphalt one-for-one for paving bitumen in a hot mix does two things at once, and both of them are usually unintended: it reduces the binder actually delivered, because a substantial part of the mass is mineral, and it simultaneously increases the filler content of the mix. The volumetrics move twice in the same direction and the result bears no relation to the approved design. The mineral has to be brought into the aggregate gradation calculation explicitly — see asphalt mix design basics for how filler enters the volumetrics.

Rock asphalt

What it is. Rock asphalt is a limestone or a sandstone that has been naturally impregnated with bitumen, usually where migrating petroleum entered a porous formation and was trapped and degraded there. The order of the words is the whole point: it is rock asphalt. The rock is the majority phase, by a very wide margin, and the bitumen occupies its pore space.

How it is won. By quarrying or mining the impregnated rock and then crushing and grinding it. The classic European deposits — the bituminous limestones of the Val de Travers area in Switzerland, at Seyssel in France and at Ragusa in Sicily — were worked into a fine powder that could be heated and compacted, and that material is the historical root of mastic asphalt technology and of the compressed rock asphalt pavements of nineteenth century European cities. In the United States, the sandstone rock asphalts of Kentucky and the limestone rock asphalt of the Uvalde area of Texas were worked on a substantial scale for surfacing.

What it contains. Bitumen content is low. Published figures for the working deposits are commonly below about fifteen percent by mass and frequently below ten, with the European bituminous limestones generally at the higher end of that and many sandstone rock asphalts lower. These are reported ranges from producer and historical literature rather than specification limits, and the bitumen content of any particular consignment is a measured number, determined by extraction, not a property of the deposit name.

What it is used for. Historically, a great deal: compressed rock asphalt carriageways, mastic asphalt footways and flooring, and waterproofing. Today its use is largely local to the deposits and specialist, with some material used as a mix additive where the host rock is acceptable as part of the aggregate skeleton. Because the host rock of most working deposits is carbonate, the mineral fraction is chemically a good partner for a bituminous binder — carbonate surfaces bond well and resist stripping — but a good filler is still a filler and not a binder.

Asbuton

What it is. Asbuton is the natural asphalt of Buton island in Southeast Sulawesi, Indonesia: a limestone naturally impregnated with bitumen. It is, in geological terms, a rock asphalt, and it is treated separately here because it is worked at a scale and traded under a name that puts it in front of international buyers far more often than the European deposits are.

How it is won. By open-cut quarrying, followed by crushing and screening to granular products of a defined size, which is how the great majority of it moves. Two deposit areas are named consistently in the technical literature: Kabungka, whose material is generally harder and lower in bitumen content, and Lawele, whose material is generally softer and higher in bitumen content. There is also an extraction route, in which the bitumen is recovered from the rock with solvent to give an extracted asbuton bitumen, and semi-extracted intermediate products between the two.

What it contains. Reported bitumen contents for the raw rock across the island’s deposits are commonly quoted in a broad band running from roughly ten to something over thirty percent by mass, varying by deposit and by working face. That band is what the technical and producer literature reports, not a specification limit, and it is wide enough that the band itself tells a buyer very little. Granular products are frequently designated by their reported bitumen content, which makes that number both the grade name and the thing most in need of independent verification. The remainder is limestone, mostly at fine sizes after crushing, which means it enters an asphalt mixture in the filler and fine aggregate fractions rather than as coarse stone.

What it is used for. In Indonesia it is used in hot and warm asphalt mixtures under the national highway specification issued by the Directorate General of Highways, as a mix additive and as a binder extender, with mix designs that account explicitly for the mineral it brings. Extracted asbuton bitumen is used as a modifier. Ask which national specification document and which edition a granular product is certified against; the answer is checkable and a supplier who cannot give it is not supplying to a specification at all.

The testing trap. Determining the binder content of a mixture containing a limestone-hosted natural asphalt is not routine. The ignition method, ASTM D6307, measures binder as loss on ignition and requires an aggregate correction factor established on the actual aggregate — and carbonate aggregates lose mass on ignition in their own right, so the correction is large and getting it wrong biases the result badly. Solvent extraction under ASTM D2172 avoids that particular error, but brings its own: the heavily aged bitumen in a natural asphalt may not extract completely, so the recovered figure can understate the binder present. Neither of these is a reason to avoid the material. Both are reasons to agree the test method, the correction factor and the acceptance basis in writing before the first delivery rather than after the first dispute.

Three independent reasons, any one of which is sufficient

• The specification reason. Penetration grades are defined for refined petroleum bitumen by ASTM D946 and EN 12591, and both require solubility of at least 99.0 percent, measured by ASTM D2042 and EN 12592. A material carrying a third of its mass as mineral, or the large majority of its mass as host rock, cannot pass that line. It is therefore not a penetration grade, cannot be certified as one, and cannot be accepted against a specification that names one.
• The arithmetic reason. A tonne is not a tonne. Where the binder fraction is a third, or a tenth, a tonne of the material delivers a third, or a tenth, of the binder that a tonne of a certified paving grade delivers, and an offer written per tonne of material conceals that entirely. Everything downstream — freight, storage, handling, mix design, binder content verification — is affected as well.
• The behaviour reason. The hydrocarbon in a natural deposit has spent geological time losing volatiles and oxidising. It is hard, high in asphaltenes and generally brittle at low temperature. In a role where hardness is what you want, that is the point of the material. In a role where you needed a 60/70, it is not the same substance in a different wrapper.

What the problematic offer looks like

The pattern is consistent, and once you have seen it once it is unmistakable:

• The material is described with a penetration grade designation attached to a natural product — natural bitumen 60/70, gilsonite 80/100, natural asphalt 60/70. No such grades exist.
• The certificate or data sheet shows penetration and softening point and very little else. There is no ash line, no solubility line, no water line, and frequently no test method named against the two figures that are shown.
• The commercial terms are the headline of the offer and the specification is an afterthought behind them. Where the terms are doing all of the persuading and the technical description is thin, the usual explanation is that the material being offered and the material being compared against are not the same kind of thing at all.
• The origin is vague, the producer is not identifiable, and the material description changes between the offer, the proforma and the draft documents.
• Independent sampling and inspection are discouraged, deferred or declined, and the seller prefers to supply a certificate rather than to allow one to be produced.

An offer that presents natural asphalt as equivalent to a penetration grade is, at best, a seller who does not understand the material they are trading. At worst it is the deliberate use of the ambiguity in the word asphalt to sell rock as binder. The buyer’s protection is identical in both cases, and it is not a judgement about the seller’s character: ask for the four numbers and the methods that produced them. The wider set of patterns, and the documentary and inspection defences against them, are covered on bitumen fraud prevention.

The four questions, in order

1. What is the binder content, and by what method? Solubility by ASTM D2042 or ASTM D7553 in current practice, or extraction by ASTM D2172 for a granular product; ASTM D4 in carbon disulfide is the historical method and the solvent has to be named either way. This is the number you are actually buying.
2. What is the ash or mineral content, and by what method? ASTM D482, or ASTM D2415, ash in coal tar and pitch, where the material is carbonaceous and higher in ash. This is the mass you are shipping, storing, handling and designing around without getting any binder in return for it.
3. What is the penetration at 25 °C, by ASTM D5 or EN 1426? If the answer is nil, the material is a hardening modifier and the conversation about penetration grades is over.
4. What is the softening point, by which method? ASTM D36 or EN 1427 for the ring-and-ball range, ASTM D3104 for material above it. A softening point without a method is not comparable between two offers, and the two methods do not produce interchangeable numbers.

Add water content by ASTM D95 wherever the material will be charged into a hot tank, because water in hot bitumen is a boil-over hazard rather than a quality question. And note that these figures must be reported on the delivered lot. A type data sheet describing what a deposit typically yields is marketing information about geology; it is not a certificate.

Documentation and logistics differ too

• Customs classification is different. Natural bitumen, asphaltites and asphaltic rocks fall under Harmonised System heading 2714, while petroleum bitumen falls under 2713.20. Two materials described loosely by the same word therefore enter a country under different headings with different documentary requirements. Confirm the classification for your consignment and your jurisdiction with your customs broker; this page states no duty rates and no classification ruling.
• Sampling is a different discipline. A liquid or semi-solid binder is sampled under ASTM D140. A granular mined solid segregates in a stockpile, in a bag and in a container, so it needs aggregate-style sampling under ASTM D75 or AASHTO T 2, with a documented increment plan. Sampling a bulk granular product as though it were a tank of binder produces a certificate that describes one scoop.
• The safety data sheet is a different document for a mined mineral product than for a hot-applied binder, and the combustible dust position for a ground asphaltite has no counterpart at all in bitumen handling.

What this site supplies, and what it does not

Stated plainly, because it is the most useful sentence on the page for a buyer trying to work out whose advice to weigh: Bitumen Asphaltive supplies refined petroleum bitumen from the Middle East. We do not supply gilsonite, Trinidad Lake Asphalt, rock asphalt or asbuton, we do not broker them, and we will not quote them.

That is not a criticism of those materials. Where a specification calls for gilsonite as a modifier, for lake asphalt in mastic work, or for granular asbuton under the Indonesian mix specification, the right answer is to buy the material as itself, from a producer of that material, against a certificate carrying the tests listed above. What is never the right answer is to accept one of them in place of a refined penetration or viscosity grade that your project specification actually requires, on the strength of a shared word in the description.