Sir: We welcome the opportunity to reply to criticism raised by Roy to our publication on the origin of the Neoproterozoic Penganga manganese formation (Gutzmer and Beukes, 1998). Roy’s "strong misgivings" with our contribution center on only one point, namely our conclusion that the todorokite-rich oxide ores mined from shallow trenches by artisan miners is of supergene origin and formed at the expense of a carbonate protore that we discovered. Our interpretation is in obvious contrast to the results of work by Roy and coworkers (Roy, 1981; Bandopadhyay, 1988, 1989, 1996; Roy...

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