Feldspathoid

The feldspathoids are a group of tectosilicate minerals which resemble feldspars but have a different structure and much lower silica content.

A notable exception where feldspathoids and quartz-bearing rocks are found together is the Red Hill Syenite.

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

Such terminology is used in the Streckeisen (QAPF) classification of igneous rocks.

This article about a specific silicate mineral is a stub.