Nepheline

Nepheline properties at a glance

Geology & background

Nepheline is a feldspathoid that crystallizes from silica-poor, alkali-rich magmas, forming in nepheline syenites, phonolites, and related igneous rocks where quartz cannot develop.

Nepheline has been important to petrologists for defining silica-undersaturated rocks, and nepheline syenite became a valued industrial raw material for glass and ceramic manufacturing.

How to identify Nepheline

• Look for gray to colorless masses with a greasy luster in silica-poor igneous rocks rather than sharp crystals.
• Nepheline is about 6 in hardness with poor cleavage and a subconchoidal fracture.
• It becomes cloudy and gelatinizes when treated with acid, helping separate it from quartz and feldspar.

Where Nepheline is found

Nepheline occurs in silica-poor igneous rocks worldwide, with notable specimen localities in Canada, Russia, Norway, Germany, the United States, and Italy.

How much is Nepheline worth?

Value depends on crystal development, color, locality, associated minerals, and overall specimen quality.

Common uses

• Glass manufacturing
• Ceramics and porcelain
• Filler and extender
• Source of alumina
• Collector specimens

Interesting facts

• Nepheline forms only in silica-poor magmas and never coexists in equilibrium with quartz.
• Its name comes from a Greek word for cloud because it turns cloudy when placed in acid.
• Nepheline is used as a raw material in glass and ceramics as an alternative to feldspar.
• The rock nepheline syenite is quarried in large quantities for industrial use.

Care & safety

Nepheline is moderately hard but brittle and can chip on edges with rough handling.

Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a proper respirator.

Related rocks & minerals

Feldspar Feldspar Group Sodalite Minerals Aegirine Minerals Biotite Minerals Jadeite Silicate Minerals Kaolinite Silicate Minerals