text: Magma exists in three main forms that vary in composition. When magma crystallizes within the crust, it forms an extrusive igneous rock. Dependent on the composition of the magma, it may form either rhyolite, andesite, or basalt. Volatiles, particularly water and carbon dioxide, significantly impact the behavior of each form of magma differently. Magma with a high concentration of volatiles has a significant reduction in temperature of up to hundreds of degrees, which reduces its inherent viscosity. The behavior of magma is also altered by varying mineralogic compositions, which is noted in Figure 1. For instance, magmatic water leads to the crystallization of several minerals abundant in hydroxyl- or halogenated-groups, including garnets. Analyses of these minerals can be used to analyze the conditions of formation in the interior of rocky planets.