Students of pegmatites and ore deposits have been impressed with the importance of certain elements, notably H, F, Cl, C, and S, whose presence has apparently aided the formation of the minerals in the suite. Such elements are known as mineralizers. Mineralizers aid in the formation of minerals in two ways. In the first place, they enter into the compositions of certain of the minerals of the suite and thus are the cause of the appearance of certain minerals uncommon to the igneous rocks. It is chiefly in this way that the mineralizers reveal their presence during mineral deposition. But their presence is also attended by an increase in the sizes of the crystals deposited. From this it is deduced that the presence of mineralizers increases the fluidity of the mineralizing solutions. Fluidity is often correlated with the volatility of the mineralizers, since the common occurrence of the elements H, F, Cl, C, and S under ordinary conditions is as the gasses H2O, F2, CI2, CO2, and SO2. The reduction of viscosity by mineralizers may be regarded as well established by field evidence. What is the explanation of the action?