Nepheline syenite

Nepheline syenite is a rock that consists largely of nepheline and alkali feldspar. The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varieties are also known.

  • Hardness is 5.5 - 6
  • Specific Gravity is 2.6+ (average)

Nepheline Syenite has been a standard in the ceramic industry for many years, and is very popular for its whiteness. Nepheline syenite melts lower than feldspars.

Like feldspar, nepheline syenite is used as a glass making, flux in tile, sanitary ware, ceramics, porcelain, vitreous and semi-vitreous bodies. It contributes high alumina without associated free silica in its raw form and fluxes to form silicates with free silica in bodies without contributing free silica itself. This stabilizes the expansion curve of the fired body. It is an excellent tile filler and melter, especially for fast firing. Nepheline syenite is valuable in glass batches to achieve the lowest melting temperature while acting as a source of alumina.

Nepheline syenite best substitute for the Bauxite. It can replace the bauxite since nepheline syenite has more alumina content, substituting it into recipes means that on one hand a lower melting temperature is achieved while on the other a more viscous melt results because of the extra alumina.

  • SiO2 60.0 56.0 41.1
  • Al2O3 23.2 24.2 34.9
  • Fe2O3 0.10 0.11
  • CaO 0 1.2
  • Na2O 10.8 7.8 15.9
  • K2O 5.1 9.1 8.1
  • LOI 0.5 1.5

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