noun
- Plural of nepheline; a silicate mineral composed of sodium, potassium, and aluminum, typically colorless or pale yellow, found in igneous rocks.
Usage: technical; mineralogy
Examples
- Nephelines are commonly found in syenite and other alkaline igneous rocks.
- The geologist identified nephelines in the thin section under the microscope.
- Nephelines crystallize in the hexagonal system and often form six-sided prisms.
- The presence of nephelines indicates that the magma was relatively poor in silica.
- Nephelines can be distinguished from feldspars by their lower hardness and different optical properties.