Nepheline syenite, also known as Neph Sy, is used to replace feldspar in the manufacture of ceramic and glass products.Nepheline syenite is a low silica, high soda and high alumina mineral.
It is chemically similar to a soda feldspar, but far more chemically complex.
It is a popular flux because of its high soda.
It has desirable properties at high temperature, like the ability to lower the fusing temperature of normally high-temper claybodies, including porcelain.
It strengthens glass, owing to its high alumina content.
Nepheline syenite reduces crazing when added to clay, but increases crazing when added to glass.