text: Rhyolitic magma is felsic and the most abundant in silica, potassium, and sodium but the lowest in iron, magnesium, and calcium. The silica composition of rhyolitic magma ranges from 65-75 wt.%. It forms in the lowest temperature range, from about 1200 °F to 1470 °F.  Rhyolitic magma has the highest viscosity and gas content. It produces the most explosive volcanic eruptions, including the catastrophic eruption of Mount Vesuvius. It forms minerals such as orthoclase feldspar, sodium-rich plagioclase feldspar, quartz, mica, and amphibole.