Synthesis of the grossularite-spessartite series¹

Although a solubility gap has been thought to exist under natural conditions between the pyralspite and ugrandite groups of garnets, an interpretation stemming from the surveys of garnet analyses by Boeke (1914) and by A. N. and H. Winchell (1951), analyses have recently been sum-marized by Frondel and Ito (1965) that indicate a probably complete series extends under some natural conditions between grossularite and spessartite. We have now synthesized the end-compositions and four compositions between Ca₃Al₂(SiO₄)₃ and Mn₃Al₂(SiO₄)₃. The solid solubility in this series under the conditions of our experiments appears to be complete.