This intrusion covers nearly 30 km2 and is composed of porphyritic and medium-grained peralkaline granites which are cut by vein-like bodies and dykes of peralkaline granite porphyry. The country rocks have been altered with the development of quartz and muscovite. The granites consist of microcline, albite, quartz, arfvedsonite, riebeckite and biotite. They are rich in accessory minerals including fluorite, zircon, including a metamict variety, orthite, monazite, ferrothorite, topaz, ilmenite, titanite, apatite. pyrite, baryte, garnet, rutile, anatase, galena, wulfenite and scheelite.