Nepheline Syenite: Antiblock and Filler, Properties and Regulatory Status

Nepheline syenite (CAS 37244-96-5) is a natural sodium potassium aluminosilicate mineral used in plastics as an antiblock additive and functional filler, mainly in polyolefin film. Because the rock is silica-undersaturated, it carries no free quartz, and that quartz-free character is the property which separates it from most mineral antiblocks used in blown film.

Nepheline syenite is authorised for EU food-contact plastics as FCM substance 684 (Ref 68125) under Regulation (EU) No 10/2011 with no specific migration limit, and ECHA CHEM holds no active REACH registration for it, because natural minerals that are not chemically modified are generally exempt from registration under REACH Annex V. Nepheline syenite is one of 8 antiblock entries in our directory of plastic additives, each with the same identity, dosage and regulatory fields.

Four facts organise everything below: irregular particles create the micro-roughness that keeps two film layers from sticking, the mineral is quartz-free with crystalline silica below 0.1 % in Covia's MINEX grades, no dosage, refractive-index figure or price for nepheline syenite is published in the sources behind this page, and the 4 minerals it competes with, diatomaceous earth, synthetic amorphous silica, talc and calcium carbonate, each carry their own EU food-contact number. Most searches for this mineral concern ceramics, glass and coatings; those markets are summarised in a single section at the end.

The identity table below collects the values that a specification, a safety data sheet and a food-contact declaration ask for.

What Is Nepheline Syenite?#

Nepheline syenite is a natural silica-undersaturated aluminosilicate rock made of the feldspathoid mineral nepheline and alkali feldspar, milled to a white powder for use in plastics. Which material does a film producer actually receive when it buys nepheline syenite? Not the quarried rock, but a milled mineral powder sold under a grade name such as Covia's MINEX, ordered by fineness and delivered to a compounder or a masterbatch plant rather than to the quarry gate.

The milled mineral powder does 2 jobs inside a plastic: it acts as an antiblock additive in film, and as a functional filler in polyolefin compounds. It is one of the 5 mineral and organic antiblock additives used in plastic film, which the family hub compares side by side. What distinguishes nepheline syenite inside that group is stated in a single property: the rock is silica-undersaturated, so it carries no free quartz, and it is supplied with a relatively low refractive index for a mineral filler.

What is another name for nepheline syenite?#

In chemical inventories nepheline syenite appears as sodium potassium aluminium silicate (natural), EC list number 609-369-8, and in plastics it is usually bought under a grade name such as Covia's MINEX. The name on the delivery note is therefore a grade name, while the name on the safety data sheet and in the customs file is the inventory name with CAS 37244-96-5.

Is nepheline syenite a feldspar?#

Nepheline syenite is not a single feldspar mineral: it is a rock that contains alkali feldspar together with nepheline, a feldspathoid, and for a plastics buyer the decisive point is the absence of free quartz. A feldspathoid forms where the melt holds too little silica to crystallise quartz, which is what "silica-undersaturated" means and why the rock is quartz-free. The practical consequence sits in the handling area rather than in the extruder: a quartz-free mineral keeps the respirable crystalline silica question out of the weighing and dosing step, which calcined diatomaceous earth grades do raise. The exposure limits behind that question are set out in the health and safety section below.

What is the composition and formula of nepheline syenite?#

PubChem records nepheline syenite under CAS 37244-96-5 with the idealised formula Al2KNaO8Si2, a nominal composition rather than a fixed molecular formula, because the material is a mixture of minerals. The word idealised carries the whole meaning here: a mixture of nepheline and alkali feldspar has no single molecular formula and no molecular weight, so the identity table above leaves that field as not applicable. An oxide analysis, the form in which mineral producers usually state composition, is not part of the verified data set behind this page, and the supplier's datasheet for the specific grade is where a formulator gets it.

How Does Nepheline Syenite Work as an Antiblock Additive?#

Nepheline syenite works as an antiblock additive because its irregular particles protrude from the film surface and create a micro-roughness that lowers the true contact area between two film layers, and with it the van der Waals adhesion that makes them stick. The same mechanism is recorded for antiblock additives in general in the Ampacet antiblock technical notes: particles standing proud of the surface hold the next layer at a distance, so the two surfaces touch on asperity tips instead of over their full area. Contact area, not particle count, is the controlled variable, which is why particle shape and top cut matter more than loading alone.

Every particulate antiblock costs optical quality, and the size of that cost tracks the refractive-index mismatch between the particle and the polymer around it. A particle whose refractive index sits close to the polymer scatters less light and adds less haze, which is why a relatively low refractive index is the selling point of this mineral and the reason it is specified for clear film. That haze trade-off is stated qualitatively here on purpose: our sources describe the refractive index of nepheline syenite only as relatively low and give no figure for it, while the competing minerals do carry published values.

What is blocking in plastic film?#

Blocking is the unwanted adhesion of two film layers that have been pressed together on the roll, and it is measured as the load needed to pull them apart. ASTM D3354-21 defines that measurement as the load in grams required to separate 100 cm2 of film contact area, with 200 g as the maximum the method reports, and ISO 11502 Method B works on a similar principle. A film that blocks stops unwinding cleanly, refuses to open on a form-fill-seal line and jams at the bagging station. The word blocking has a narrow meaning in film converting, and the glossary entry gives it.

What Are the Physical Properties of Nepheline Syenite?#

Nepheline syenite is supplied as a white powder that is quartz-free, with crystalline silica below 0.1 % in Covia's MINEX grades and a relatively low refractive index for a mineral filler. The properties verified for this page are listed in the table below, together with the fields that carry no value in our sources.

Five of the values a film formulator compares first, median particle size, top cut, specific gravity, Mohs hardness and a numeric refractive index, are not published in the sources behind this page, so the table names the gap instead of filling it with a plausible number. Those 5 values decide how a grade behaves on a blown-film line, and the producer datasheet for the specific grade is where they belong. Every figure printed further down this page for hardness, particle size or refractive index belongs to a competing mineral and is labelled with that mineral's name.

Which Polymers Use Nepheline Syenite, and at What Dosage?#

Nepheline syenite is used in polyolefin film, where it serves both as an antiblock additive and as a functional filler. Polyolefin film means LDPE and LLDPE blown film in the first place, the film types where blocking is a daily production problem and where a clear skin layer has to survive the antiblock that protects it.

The comparator rows carry the levels published for competing minerals, not for nepheline syenite.

No published dosage level for nepheline syenite appears in the sources behind this page, and no published level in our sources fixes a ppm window for it. For orientation, the trial ranges Ampacet reports for the minerals it competes with are 2,500 to 10,000 ppm for diatomaceous earth and talc and 2,500 to 20,000 ppm for calcium carbonate, which needs 250 to 300 % more material to reach the same effect. Typical additive dosage levels for every additive family, in ppm and wt%, are collected in one table.

Mineral antiblocks reach the extruder as an additive masterbatch rather than as a free-flowing powder in most film plants, because a 2 µm to 10 µm mineral dust dispersed into a carrier resin dose-feeds more accurately and disperses better than the same powder metered neat. The let-down ratio used for antiblock masterbatch is not established in our source library and is therefore not stated here.

Nepheline syenite in polyolefin film#

In polyolefin film, nepheline syenite sits in the same additive package as a slip agent at 0.05 to 0.12 wt%, a polymer processing aid, an antistat and, in food packaging, an antifog additive. The antiblock share of that package is where the mineral works, in the skin layer of a coextruded structure rather than in the core, because only particles in the outer layer reach the surface where blocking happens. The complete package for this film type is set out under additives for packaging film.

Our source library records nepheline syenite in polyolefin film and in no other polymer: there is no record of it in PVC, in PET or in engineering polymers, so this page claims polyolefin film only rather than implying breadth the data does not support. Our sources record polyolefin film only; the wider PE formulation is covered under additives for polyethylene.

Nepheline syenite as a functional filler#

Nepheline syenite is also used as a functional filler, which means it is added for a property it brings rather than only to displace resin volume. In the polyolefin compounds recorded in our source library, the property it brings is the combination that also drives its antiblock use: a relatively low refractive index, which limits the optical penalty of a mineral loading, and a quartz-free composition, which keeps the respirable-silica question out of the compound. A functional filler is judged on what it adds, which is the distinction the hub on fillers for plastics draws between inert extenders and functional grades. The scratch resistance, weatherability and brightness claims that appear on producer pages come from coatings data and are not stated here as plastics performance.

What Is Nepheline Syenite Used For in Plastics?#

In plastics, nepheline syenite has 2 jobs: it is an antiblock additive that keeps film layers from sticking, and a functional filler in polyolefin compounds. The 2 recorded plastics applications are listed below.

• Antiblock in polyolefin film. Irregular particles in the skin layer create surface micro-roughness, cut the contact area between adjacent layers and so cut the force needed to separate them, with a smaller clarity penalty than a high-refractive-index mineral imposes.
• Functional filler in polyolefin compounds. The same milled powder is loaded as a mineral filler that is quartz-free and relatively low in refractive index, so it adds mineral content without the optical cost of a calcite or the silica question of a calcined grade.

Both jobs use one and the same grade property set, which is why a film producer often buys a single mineral for both functions instead of running an antiblock and a filler in parallel. What the material is not used for in plastics matters equally: no heat-stabilising, no light-stabilising and no flame-retardant function is recorded for it, and nothing in our sources support a reinforcement claim. Outside plastics, ceramics, glass and coatings are the dominant markets for this mineral, and they are summarised at the end of this page.

How Does Nepheline Syenite Perform in Film?#

Antiblock performance is judged on 3 measurements: blocking force by ASTM D3354-21, coefficient of friction by ASTM D1894-24 or ISO 8295, and haze by ASTM D1003-21. Blocking force is the load in grams needed to separate 100 cm2 of film contact, capped at 200 g by the method. Coefficient of friction results depend on the time between film production and the test, because a migrating slip agent is still moving to the surface while the film ages. Both methods are described on coefficient of friction and blocking.

Haze rises with the refractive-index mismatch between particle and polymer, which is why the refractive indices of the competing minerals matter: 1.459 for precipitated silica, 1.58 for talc and 1.6584 for calcite at 589 nm. Our sources describe the refractive index of nepheline syenite only as relatively low and give no figure, so this page carries no haze number, no blocking-force number and no coefficient-of-friction number for the mineral. The haze procedures and the 30 % diffusing threshold are explained under haze and clarity measurement. A grade trial on the target film structure, run against the incumbent antiblock at equal loading, is what closes that gap in practice.

How Does Nepheline Syenite Interact with Slip, Antistatic and Processing Additives?#

Mineral antiblock particles compete for the same additives that need to reach the film surface, and the effect is documented for silica: it adsorbs slip agents and antistats, and erucamide adsorbs onto antiblock particles. Mineral particles and slip additives share the film surface, and that is where most coefficient-of-friction complaints start. Whether nepheline syenite behaves the same way is not documented in our sources, so the 3 interactions below are stated for the minerals on which they were measured.

Three interactions matter in a film formulation. Erucamide adsorbs onto antiblock particles, which is why its bloom curve changes with the antiblock choice.

• Slip adsorption. Synthetic silica adsorbs slip agents, and the erucamide plus silica pair lowers the coefficient of friction in polypropylene more than either component alone; erucamide at 0.05 to 0.12 wt% gives most of its coefficient-of-friction drop within 24 to 48 hours and reaches its final value after 7 to 10 days, so a change of antiblock shifts that whole bloom window.
• Antistat adsorption. Migrating antistats are retarded by the same adsorption on synthetic silica, so the surface resistivity of a freshly produced film can lag behind its specification.
• Stabiliser adsorption. Talc, kaolin and silica adsorb antioxidants and hindered amine light stabilisers at acid surface sites, with a measurable loss of stabiliser activity in the compound.

Blown-film lines usually run a mineral antiblock alongside fluoropolymer processing aids, which is formulation context rather than an interaction claim: no interaction between nepheline syenite and a polymer processing aid is established in our source library.

What Is the Regulatory Status of Nepheline Syenite?#

Nepheline syenite is authorised for EU food-contact plastics as FCM substance 684 with no specific migration limit, is not a Substance of Very High Concern and has no active REACH registration, because unmodified natural minerals are generally exempt under REACH Annex V (status 22 September 2026). The full matrix, instrument by instrument, is set out below.

Three of the 10 cells above are open rather than negative, and the difference is material: "status being verified" means our sources record no entry either way, not that the mineral is prohibited. How registration, the Candidate List and the Annex V exemptions apply to additives is set out under REACH and plastic additives.

Is nepheline syenite registered under REACH?#

No: no active REACH registration for nepheline syenite was found in ECHA CHEM, because natural minerals that are not chemically modified are generally exempt from registration under REACH Annex V. Nepheline syenite (EC 609-369-8) sits in that group together with feldspar (EC 270-666-7), both of them natural minerals carrying a list number and no dossier. An EC list number is not a registration number, so a supplier cannot quote a REACH registration number for this material, and the exemption route rather than a registration number is what an audit file records. The specific determination that a given grade qualifies under Annex V stays with the supplier who places it on the EU market.

Is nepheline syenite allowed in food-contact plastics?#

Yes, in the EU: nepheline syenite is listed in Annex I of Regulation (EU) No 10/2011 as FCM substance 684 (Ref 68125) with no specific migration limit, so the overall migration limit of 10 mg/dm2 is what applies. The Union list, the overall migration limit and the group restrictions are explained on EU 10/2011.

Every mineral antiblock in commercial use carries its own entry in that same Union list, which is what makes the food-contact comparison decidable: synthetic amorphous silica is FCM 504 (Ref 86240), diatomaceous earth FCM 707 (Ref 46375), soda ash flux-calcined diatomaceous earth FCM 734 (Ref 46380), talc FCM 615 (Ref 92080), nepheline syenite FCM 684 (Ref 68125) and calcium carbonate FCM 21 (Ref 42500). None of the 6 carries a substance-specific migration limit, so the choice between them is a technical and occupational-hygiene decision rather than a food-contact one.

Is nepheline syenite FDA approved?#

Our sources record no US FDA clearance for nepheline syenite: it is not among the minerals listed in 21 CFR 178.3297, which is not the same as a prohibition. That section lists mica, china clay, barium sulfate, bentonite, calcium carbonate, calcium silicate, diatomaceous earth, talc and silica as colorants for polymers, and nepheline syenite is absent from that closed list. Which 21 CFR sections cover mineral additives is listed under FDA food contact rules.

Is Nepheline Syenite Toxic? Health and Safety Profile#

Nepheline syenite has no harmonised EU hazard classification in our sources, and in the PubChem notification aggregate only a minority of notifiers report H335, may cause respiratory irritation. A notification aggregate is self-classification by the companies that place the substance on the market, so it records what suppliers declare rather than a legal classification under Regulation (EC) No 1272/2008.

The real question behind "is nepheline syenite toxic" is dust exposure in the weighing, dosing and cleaning steps, not migration out of a finished film. Mineral antiblock dust is an occupational exposure question, and the reason nepheline syenite is specified in some plants is that it is quartz-free, with crystalline silica below 0.1 % in Covia's MINEX grades, while calcined diatomaceous earth grades can contain crystalline silica. The 3 documented points that govern handling are listed below.

• Classification. No harmonised classification is recorded in our sources; a minority of notifiers report H335 (may cause respiratory irritation) in the PubChem aggregate.
• Dust exposure. Respirable crystalline silica carries an EU occupational exposure limit of 0.1 mg/m3 under Directive (EU) 2017/2398, an OSHA permissible exposure limit of 50 µg/m3 with an action level of 25 µg/m3, and a California Proposition 65 listing dated 1 October 1988.
• Comparison. Nepheline syenite is quartz-free at below 0.1 % crystalline silica, while calcined diatomaceous earth grades contain crystalline silica and are handled against those limits.

No LD50, no NOAEL and no inhalation study for nepheline syenite is part of the verified data set behind this page, so no toxicological threshold is stated here and the words safe, non-toxic and inert are not used. Mineral antiblocks do not appear on the lists of chemicals of concern in plastics that drive additive substitution, which is the practical reason the substitution pressure in film formulation runs toward the plasticisers and the halogenated stabilisers rather than toward the mineral particles.

What Is a Substitute for Nepheline Syenite?#

The 3 substitutes recorded for nepheline syenite are synthetic amorphous silica, diatomaceous earth and talc, with calcium carbonate and organic beads as the wider alternatives in the antiblock family. The 5 antiblock minerals are compared below on the 5 criteria that decide a substitution: identity, refractive index, published level, food-contact entry and crystalline-silica position.

Levels are the ranges published for each mineral by Ampacet or in the cited reviews. No level is published for nepheline syenite.

The synthetic and natural silica grades are compared in detail under silica antiblock.

Nepheline syenite vs diatomaceous earth#

Diatomaceous earth is the efficiency benchmark among the mineral antiblocks, at 2,500 to 10,000 ppm in the Ampacet trials, but it is abrasive at Mohs 5.5 to 6, its top cut can reach 44 µm against a typical 25 µm film, and its calcined grades contain crystalline silica. Diatomaceous earth carries the crystalline-silica question in its calcined grades, and it also carries 0.5 % to 2 % iron oxide, which can accelerate polymer degradation in a hot melt.

Nepheline syenite takes the counter-position on exactly those 3 points: it is quartz-free with crystalline silica below 0.1 % in the MINEX grades, and no iron-driven degradation effect is recorded for it in our sources. The caveat belongs in the same paragraph: no efficiency figure comparable to the 2,500 to 10,000 ppm window of diatomaceous earth is published for nepheline syenite, so the trade is a documented hygiene advantage against an undocumented loading.

Nepheline syenite vs synthetic amorphous silica#

Synthetic amorphous silica is the most efficient antiblock in the published record: high pore-volume grades work at 1,000 to 1,500 ppm in 35 µm films, as Van Essche, Kromminga and Schmidt reported in the Journal of Plastic Film and Sheeting in 2000. Precipitated silica antiblock generally runs below 0.5 wt%, its refractive index of 1.459 sits below that of every natural mineral in the comparison, and it is listed as FCM 504 (Ref 86240) in the Union list. Precipitated silica is the efficiency benchmark, at levels below 0.5 wt%.

Efficiency comes with a formulation cost that is documented for silica alone: synthetic silica adsorbs slip agents and antistats, so erucamide bloom and antistatic build-up both shift when a silica antiblock is used. No comparative adsorption measurement for nepheline syenite exists in our sources, which means the mineral cannot be claimed to avoid that cost, only that the cost has not been measured on it.

Nepheline syenite vs talc#

Talc is the low-cost mineral antiblock, at 2,500 to 10,000 ppm and up to 5 wt% in PP blown film for food packaging, but it carries a regulatory question that nepheline syenite does not. The ECHA Risk Assessment Committee opinion of 20 September 2024 proposes classifying talc as Carc. 1B (H350) and STOT RE 1 (H372); this is a proposal, and talc is not in CLP Annex VI as of 1 July 2026. IARC placed talc in Group 2A in 2024, and California Proposition 65 lists only talc containing asbestiform fibres, listed on 1 April 1990.

Two technical differences sit beside that regulatory one. Talc is a plate with an aspect ratio of 5 to 40 and a refractive index of 1.58, so it roughens a surface efficiently but scatters more light than a low-refractive-index mineral, and its Lewis-acid surface sites can adsorb antioxidants and hindered amine light stabilisers. Grades, levels and the food-packaging position are covered under talc antiblock.

Who Supplies Nepheline Syenite? Grades and Producers#

Nepheline syenite for plastics comes from a small number of deposits: Covia mills it at Blue Mountain in Ontario and sells it as MINEX, and Sibelco mines it at Stjernøy in Norway. That short list is what makes nepheline syenite suppliers a different sourcing problem from silica or calcium carbonate, where dozens of producers compete on freight distance.

Grade designations, particle-size cuts and food-contact statements per grade are not part of our verified data set; request them from the producer.

More mineral producers, their plants and their certifications are listed in the directory of mineral filler suppliers.

Buyers should ask each of the nepheline syenite manufacturers for 4 things before a trial: the median particle size and top cut of the grade, the crystalline silica content with its test method, the food-contact statement referencing FCM 684, and whether the material is offered as powder or as an antiblock masterbatch. Those 4 answers decide whether a grade fits an existing film line, and 2 of them are exactly the values that no public source publishes.

How much does nepheline syenite cost?#

No published price series for nepheline syenite appears in our sources, so this page states the price context of the minerals it competes with and the factors that move a quotation instead of a number. The one mineral-antiblock price datum in our source library belongs to a different mineral: the US average diatomite price was USD 590 per tonne free on board plant in the 2024 estimate of the USGS, with filtration grades at about USD 790 per tonne. That is a diatomite figure and it is not a nepheline syenite price.

Four drivers move a nepheline syenite quotation: grade fineness, because finer cuts cost more milling energy per tonne; packaging and freight, which weigh heavily when only 2 deposits supply the market; the choice between direct powder purchase and an antiblock masterbatch, which adds a carrier resin and a compounding step; and order volume. Price guides for the additives that do have published series sit under plastic additive prices.

How Does Nepheline Syenite Fit into the Antiblock and Filler Families?#

Nepheline syenite is the third of the 5 antiblock types used in plastic film, between talc and calcium carbonate, and it belongs at the same time to the mineral fillers. Dual family membership is what makes this substance unusual in our substance directory: most additives serve one function, while this one is bought as an antiblock and loaded as a functional filler from the same bag. The 5 types of antiblock additives run from silica to organic beads on the family hub, and the mineral fillers hub treats the same powder from the loading and property side.

Mineral antiblocks and their particle shapes#

Particle shape is what separates the mineral antiblocks: irregular particles create more surface roughness per unit of loading than blocky ones, which is why calcium carbonate needs 250 to 300 % more material than diatomaceous earth or talc to reach the same effect. The 4 shapes in commercial use are the irregular porous frustule of diatomaceous earth, the irregular grain of nepheline syenite, the plate of talc at an aspect ratio of 5 to 40 and the blocky grain of calcium carbonate at an aspect ratio of 1 to 3. Particle shape, aspect ratio and surface area are defined under filler properties.

Where nepheline syenite is used outside plastics#

Most of the world's nepheline syenite never reaches a plastic: ceramics, glass and coatings are the dominant markets, which is also why most searches for this mineral are about glazes and glass batches rather than film. Our source library records those 3 markets as a list of applications and nothing further, with no mechanism, no firing temperatures and no market shares, so this page names them and stops there.

That split explains the search picture around the term. The encyclopedia and geology pages that rank for "nepheline syenite" answer a rock question, the ceramics suppliers answer a glaze question, and neither answers the question a film formulator asks, which is what the mineral does between two layers of polyethylene. This page answers the plastics question only.

Is nepheline syenite dangerous?#

The documented hazard is dust exposure rather than the mineral itself: a minority of notifiers report H335, may cause respiratory irritation, and the material is quartz-free, with crystalline silica below 0.1 % in Covia's MINEX grades. Handling follows the dust-control practice used for any fine mineral powder, and the occupational limits that apply to respirable crystalline silica are set out in the health and safety section above.

Is nepheline syenite valuable?#

Nepheline syenite is an industrial mineral, priced by the tonne rather than as a specimen, and its value to a film producer lies in being quartz-free with a relatively low refractive index. No price series for the mineral is published in our sources, so its value here is described by what it replaces: a calcined grade that carries crystalline silica, or a higher-refractive-index mineral that costs film clarity.