The American Journal of Science, Band 267

activity coefficients albite almandine aluminum silicate amphibolite analcite analysis andalusite aqueous assemblages basaltic biotite buffer calcite calculated chemical chlorite chloritoid coexisting composition concentration constant Cooksburg cordierite corundum crystals curve deformation determined diagram entropy equation equilibrium experimental facies feldspar fluid fold formation fossil garnet gedrite Geology glass grains granite H₂O hematite high temperatures hydrothermal inclusions indicate invariant point ionic ions iron jadeite Jour kyanite lava liquid magnesium melting metamorphic metasomatism minerals molal muscovite NaCl nepheline olivine organic layer orthopyroxene pelitic phase phenocrysts plagioclase polymorphs porphyry Portland Point present pressure quartz range ratio reaction relations Riphean rocks runs samples sanidine schist sediment sequence shale shown in figure sillimanite SiO2 solubility solution species specimens stability staurolite stromatolites sulfide Survey tion Triassic triple point tuff univariant values vapor velocity volcanic volume wt percent X-ray zone