This is true of many gabbros, aplites and granites. They include rhyolitic volcanic rocks, gabbros, carbonatites and kimberlites. The Nilgiri system comprises charnockites ranging from granites to gabbros. Less suitable for life are the layers of sheeted dikes and gabbros underneath. These subgroups are the Glen Mountains Layered Complex and the Roosevelt Gabbros. The geology consists of a dark breccia of gabbros and dolerites intruding Archaean gneiss. It comprises pillow basalts, dolerites, gabbros, ultramafic rocks, cherts and massive sulfides. The Saouda Series is intruded by younger basalts, anorthosite and gabbros along with serpentinite. The host rocks tend to be gabbros to syenite associated with intruding limestone. The rocks composing Piz Bernina are mostly diorites and gabbros. The seamount is composed of gabbros of the oceanic crust, serpentized rocks and alkaline basalts. Cumulate gabbros are more properly termed "pyroxene-plagioclase adcumulate". Their essential minerals are pyroxene, plagioclase and garnet&colon; chemically they resemble the gabbros.