Nepheline Syenite

WHAT IS
Nepheline Syenite?

Nepheline syenite is an anhydrous-sodium-potassium-aluminosilicate that is a natural, versatile, clean mineral functional filler, which is the high-quality alternative to ground crystalline silica or microcrystalline silica. With similar and, often superior, physical properties, nepheline syenite is the filler replacement you can count on.

Nepheline syenite has low oil absorption and surface area. The low surface area and alkali-aluminosilicate surface chemistry contribute to the ease of wetting, rapid dispersion, and high loading with low viscosity build. Nepheline syenite is also whiter and brighter or less yellow than most mineral powders, yielding cleaner, brighter colors or transparency when required.

Covia’s distinctive nepheline syenite adds performance value to many applications, including plastics, elastomers, paints, coatings, adhesives, sealants, inks, food and beverage packaging, medical supply packaging, greenhouse film, and technical film. This versatifle functional filler enhances durability with outstanding mechanical properties, such as scratch and mar resistance, while improving optical properties with remarkable UV resistance.

PHYSICAL AND CHEMICAL PROPERTIES

Covia’s distinctive nepheline syenite adds performance value to many applications, including plastics, elastomers, paints, coatings, adhesives, sealants, inks, food and beverage packaging, medical supply packaging, greenhouse film, and technical film. This versatile functional filler enhances durability with outstanding mechanical properties, such as scratch and mar resistance, while improving optical properties with remarkable UV resistance.

Silica content: Silica deficient

Silica deficient

Nepheline syenite does not require labeling for the presence of crystalline silica which gives it an industrial hygiene advantage over many minerals that do. Geologically, the feldspathic combination known as nepheline syenite can only form in a silica (SiO2) deficient metamorphic environment as it slowly cooled and crystalized. The SiO2 reported the chemical formula is not “free-silica,” because the silicon and oxygen are combined with aluminum as well as sodium/potassium, and no combinations of SiO2 or quartz are detectable in the ore body.

Silica deficient

Distribution sizes: 1.2 mm down to ultrafine grades

Distribution sizes

A wide range of particle size distributions are available to suit nearly every end use, and topsize need from a coarse rough texture to ultra smooth. The coarser industrial grades start at a particle topsize of about 1.2 mm and go all the way down ultrafine grades of only a few microns, with all size in between available to match your specific particle size distribution requirements.

Distribution sizes

Hardness: 6 on Mohs scale

Hardness

Nepheline syenite possesses a Moh hardness of 6 on the scale of 1-10 used to classify industrial minerals for relative hardness and compressive strength. It is considered moderately hard and is useful for increasing the overall compressive strength, scratch resistance, mar and abrasion resistance when used as a reinforcing filler in mostly polymer and coatings systems, but not so hard that it becomes overly abrasive to processing equipment.

Hardness

Bulk density: Varies by size

Bulk density

Bulk density of standard micronized nepheline syenite powders with 400-mesh to 100 mesh topsize have bulk densities that range from 40 lbs/ft3 to about 75 lbs/ft3, respectively. Larger aggregate nepheline syenite grades with topsize approaching 1.2 mm or 16 mesh would have bulk density approach 90 lbs/ft3. It is necessary to know the bulk density so engineers know what size silos and bins to install to store specific weights of nepheline syenite materials used in production. Bulk density is expressed in kilograms per cubic meter (Kg/m3) or pounds per cub foot cubic (lbs/ft3 ).

Bulk density

Moisture content: 0.02% to 0.3%

Moisture content

There is no moisture present with within the mineral complex. Surface moisture is typically very low for the coarser industrial grades (< 0.1%) and low for micronized grades typically reported in the 0.1 to 0.3% range. Covia also offers hydrophobically treated nepheline syenite powders for moisture sensitive applications and increased moisture and water resistance where desired.

Moisture content

Specific gravity: 2.61 g/cc

Specific gravity

Nepheline syenite has a specific gravity of 2.61 grams per cubic centimeter (g/cc). This is similar to most naturally occurring silica and silicates that possess specific gravities ranging from 2.5 to 2.8 g/cc. It is slightly lower density than crystalline silica (2.65), kaolin (2.65) and talc (2.7).

Specific gravity

Color: White

Color

Covia nepheline syenite powders possess some of the highest whiteness and brightness of all nepheline syenite sources in NAM and globally. Micronized fillers have L* powder whiteness powder ranging from 95 to 97 on scale of 0 to 100. This corresponds to a GE brightness from 84 to 94 which is used by the paper industry. The material becomes whiter with reduced particle size. Given the translucent properties of Covia’s nepheline syenite and color quality, It is useful to produce clean and crisp colors or attractive whites.

Color

Iron: 0.05 to 0.10%

Iron

Iron oxide content for Covia nepheline syenite grades, after processing, are consistently low in the range of 0.05 to 0.10 %. The low iron content is desirable in nearly all glass, ceramic, building product and coatings applications for aesthetics and durability. Covia’s nepheline syenite deposit and grain structure lend themselves especially well to the removal of iron bearing and mineral impurities like biotite and epidote, or non-ferrous minerals like sodalite, analcime, or muscovite. The consistency and structure allow for iron impurities to be reduced to levels two to three times lower than most nepheline syenite deposits found around the world contributing to our reputation for consistency and quality.

Iron