The properties of interlayer or nonexchangeable potassium in micaceous minerals obtained from two soils were examined as compared with that of muscovite, 2M-type dioctahedral mica, and sericite, 1M-type one, by following methods: with sodium tetraphenylborate (NaTPB) solution, and molten lithium nitrate, interlayer potassium was extractedfrom minerals and changes of thier basal spacing were observed by X-ray diffraction analysis.
With both treatment, interlayer potassium of soil minerals was released more difficult than that of sericite, but so easy as that of muscovite. However, the mode of potassium release from soil minerals was rather similar to the case of muscovite. The result of X-ray diffraction analysis also showed the similarity between soil minerals and muscovite, but changes of the basal spacing in soil minerals seemed to be slightly diffused by co-existance of 2: 1 type minerals such as vermiculite.
Above results suggest that mica minerals in soils may be 2M-type dioctahedral micas. They have remained for a long time because of the strong stability against soil weathering reactions.
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