What is a tephrite in geology ?

Tephrite : definition

Streckeisen diagrams (or QAPF diagrams) - Classification of plutonic and volcanic rocks
A tephrite is an undersaturated volcanic rock, gray in color, microlic or porphyritic, with plagioclase (andesine, labrador), rare sanidine, feldspathoid, pyroxene (augite), amphibole (hornblende), but without olivine.

The varieties of tephrite are defined according to the nature of the feldspathoid : nepheline (vesuvite), hauynite (ordanchite, from Banne d'Ordanche in Mont Dore).

Tephrites form flows that they frequently share with basalts or phonolites. The plutonic equivalent of tephrite is essexite.
Hornblende syenite from USA

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