Weathering of Mica by Fungi

Abstract Three trioctahedral micas and one dioctahedral mica (1–5µ size fractions) were used as sources of K + for seven fungi grown in nutrient solution buffered at pH 6. Vermiculite formed from the mica. The mechanism involved was exchange of solution Na + for mica K + , with the fungi functioning as K + ‐sinks. Reducing the concentration of solution Na + from 0.054 M to 0.017 M resulted in decreased rate of utilization of mica K + . Growth of fungi and release of K + were greater for trioctahedral micas than for the dioctahedral mica and generally followed the K + ease‐of‐release pattern established using sodium tetraphenylboron and NaCl solutions. The fungi differed in their capacities to promote the mica‐to‐vermiculite transition, and this was probably due mainly to their relative effectiveness as K + ‐sinks.