The mineralogy seems similar with modern rhyolites and dacites. Its sediments consist mainly of shales and greywackes with intercalated rhyolites and carbonates. This includes shales, siltstones, sandstones and some minor rhyolites and tuffs. There are examples known of highly sheared granites which can be mistaken for rhyolites. The second and third intervals saw eruptions of great quantities of rhyolites. Partial melting may also be the source of the rhyolites. The sequence includes rhyolites, agglomerates and tuff. The Sergeyevskoye deposit of ceramic rhyolites is located in Partizansky District. Most of the rhyolites are characterized by large amounts of pyroxene. The rocks were mainly igneous in nature, including granites, andesites, dacites, rhyolites, mafic dykes, etc. The Holocene rhyolites are glassy and contain few crystals. The 'Uriconian Volcanics' include rhyolites, tuffs and agglomerates. Rock types include quartzite, diorite, Devonian rhyolites, rhyo-dacites, Silurian phyllites, slates, siltstones and tuff limestones. All Tertiary acid lavas are included under rhyolites. They are intrusive into the rhyolites with development of fine grained granophyre at the contact.