Koksalinskii is emplaced in Ordovician and Devonian extrusive formations. It has an elongate, dyke-like form and occupies an area of about 15 km2. Biotite granites are developed in the northern and southern parts of the massif and in the central area are riebeckite and aegirine-riebeckite varieties that gradually grade into the biotite granite. Along the eastern margin there is a narrow strip of riebeckite and hastingsite granites. There are early dykes of granite and aplite and later ones of syenite and diorite porphyry.