feldspathoid

It is a feldspathoid and a member of the sodalite group.

A normative feldspathoid classifies a rock as silica-undersaturated; an example is nephelinite.

F (Foidite) (Name according to dominant feldspathoid when possible.

Nepheline is the main feldspathoid.

A light, relatively hard yet fragile mineral, sodalite is named after its sodium content; in mineralogy it may be classed as a feldspathoid.

The mineral assemblage consists of essential alkali feldspar; relatively minor plagioclase and quartz or a feldspathoid such as nepheline may also be present.

Silica-undersaturated mafic igneous rocks contain magnesian olivine but not magnesian orthopyroxene, and/or a feldspathoid.

Foid, contraction of the term feldspathoid, is applied to any igneous rock containing up to 60% modal feldspathoid minerals.

Nepheline is a feldspathoid, a solid-solution mineral, that does not coexist with quartz; rather, nepheline would react with quartz to produce alkali feldspar.

Felsic A mnemonic adjective derived from feldspar + lenad (feldspathoid) + silica + c, and applied to those minerals (quartz, feldspars, feldspathoids, muscovite) as a group.

Basanite, transitional basalt, and alkali olivine basalt groundmass contain plagioclase, clinopyroxene, Fe-Ti oxides, feldspathoid, olivine, and apatite.

Potentially, a mass of residual melt, and crystals of K-feldspar and feldspathoid, was buoyant relative to the surrounding pyroxenite, which allowed it it to rise and partly intrude the syenites.

At very low degrees of partial melting a silica undersaturated melt is produced, forming a nepheline syenite, where orthoclase is replaced by a feldspathoid such as leucite, nepheline or analcime.