Feldspathoid

tectosilicate

nepheline

Feldspathoids form a family of tectosilicate minerals which resemble feldspars but have a different structure and much lower silica content. They occur in rare and unusual types of igneous rocks, and are not found in rocks containing primary quartz.
Feldspathoids are common constituents of basalt.
They also may be found in diorite and gabbro.
nepheline is the commonest feldspathoid.

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