Abstract
Mica nodules from the Dutoitspan and Wesselton mines, Kimberley can be divided into two groups: diopside-phlogopite nodules and potassic richterite-phlogopite nodules. The latter is characterized by the presence of abundant potassic richterite (less than 50% by volume) and large size of the crystals (up to 1 cm in length). It seems this type nodule is the first finding.
Phlogopites and potassic richterites show a rather wide variations of major elements they have low Al2O3 and high Fe2O3, with Fe+3 in addition to Al+3 in the tetrahedral sites. It is believed that the mica nodules would be produced from kimberlitic and related magmas under moderate temperature and pressure conditions.
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Aoki, Ki. Phlogopites and potassic richterites from mica nodules in South African kimberlites. Contr. Mineral. and Petrol. 48, 1–7 (1974). https://doi.org/10.1007/BF00399105
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DOI: https://doi.org/10.1007/BF00399105