Aegirine-augite syenite occurs as small hillocks or dome-shaped mounds around Gundlapalle, Satehnapalli Taluk, Guntur District. It is composed of abundant microclineperthite, subordinate oligoclase, aegirine-augite, occasional ferro-actinolite, katophorite, barkevikite and accessories like calcite, chlorite, apatite, zircon, sphene, fluorite, pyrites and iron ore. Aegirine-augite syenite is an alkaline rock, similar to fenite in its mineral assemblage and it has undergone alkali metasomatism to give rise to the soda amphiboles. Evidences are given in support of the above conclusion.