Aug 04, 2022 · Rhyolitic magma is high in potassium and sodium but low in iron, magnesium, and calcium. It occurs in the temperature range of about 650oC to 800oC (1202oF to 1472oF). Both the temperature and mineral content of magma affect how easily it flows. The viscosity (thickness) of the magma that erupts from a volcano affects the shape of the volcano.
Olivine is the name given to a set of silie minerals which have a generalized chemical composition of A2SiO4. In that generalized composition, "A" is generally Mg or Fe, however in unusual situations can be Ca, Mn, or Ni. The chemical composition of most olivine falls somewhere between pure forsterite (Mg2SiO4) and pure fayalite (Fe2SiO4).