Pyrope in Kimberlite

The chemical composition of kimberlite pyropes from Kimberley, South Africa, from Trebenice, Czechoslovakia and from Northern Arizona, have been determined by electron probe microanalysis. The most common garnet in each locality is a magnesium-rich chrome pyrope (approximately pyrope₇₀almandine₁₅grossular₅uvarovite₅espessartine₁). The Kimberley pyropes have a grossular content of approximately 8 mole percent over a wide range of Mg/Fe ratios, whereas in the Czechoslovakia and Arizona pyropes grossular content increases with decreasing Mg/Fe ratio. Pyrope analyses for each occurrence do not plot in discontinuous groups but define a continuous series of compositions.