Lava Vesuvius between May 14 and June 4, 1737. Serao described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of the volcano following heavy rain. The composition of almost all lava of the Earth's crust is dominated by silicate minerals, mostly feldspars, olivine, pyroxenes, amphiboles, micas and quartz. Igneous rocks, which form lava flows when erupted, can be classified into three chemical types: "felsic", "intermediate", and "mafic" (four if one includes the super-heated "ultramafic"). These classes are primarily chemical, however, the chemistry of lava also tends to correlate with the magma
Ringing rocks of symmetry. The overall geometry is cylindrical, with an average diameter of one kilometer. The pluton consists of two major units: an inner core of quartz-bearing felsic units with a diameter of 600 meters and an outer mafic unit composed of coaxial concentric layers. In map view, the complex has a bulls-eye configuration. The outer zone of the pluton consists of two alternating mafic hybrid rock types. In chemical analysis the rocks are nearly identical; however, the early stage minerals, olivine and pyroxene, were preserved in one and not the other, giving the rocks sharply different weathering properties. The rock