What is essexite in geology ?

Essexite : definition

Streckeisen diagrams (or QAPF diagrams) - Classification of plutonic and volcanic rocks
Essexite is a grainy, undersaturated, dark gray plutonic rock composed of plagioclase (andesine and labrador), nepheline, augite and brown amphibole (barkevicite), sometimes of biotite, titanite and rarely of orthoclase or analcime. It is also sometimes referred to as feldspathoid monzodiorite and monzogabbro.

It is a rare rock accompanying gabbros and theralites in basic complexes. Its volcanic equivalent is tephritis.