One large and a number of smaller bodies extend north-south over some 40 km and cover about 26 km2. They comprise principally a variable suite of nepheline syenites including variants rich in sodalite and arfvedsonite. Some varieties have a strongly developed gneissose fabric. Biotite is the usual mafic mineral and cancrinite is abundant. Sodalite comprises more than 30% of some rocks and appears to have replaced nepheline. The feldspar is essentially perthite. Small plugs and dykes of porphyritic biotite tinguaite occur up to 12 km from the principal intrusions. Syenites, some with a little quartz, also occur and may be (?)fenites.