MODERN mineralogical literature contains many papers on interstratified minerals, hut very few in which 1:1 (one tetrahedral per one octahedral) layers participate in the interstratification. Brindley and Gillery (1954) reported a mixed-layer kaolin-chlorite, and Sudo and Hayashi (1956) and subsequently Shimoyama et al. (1969) described randomly interstratifled kaolin-mont-moriUonite from an acid clay in Japan. In the last mentioned cases, 2:1 (two tetrahedral per one octahedral) expanding

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... s of montmoriiionite were distinguished from l : l layers, but no differentiation was made between halloysite, metahalloysite and kaolinite. In Jeglova, Lower Silesia, western Poland, kaolin clay and well developed quartz .crystals fill veins and cavities in metamorphic shield rocks associated with the granite intrusion known as the "Strzelin intrusion". This kaolin is a very plastic clay, fine grained and mostly white in color, but sometimes yellow or brown depending on the iron content. From the chemical composition and differential thermal curve (Morawiecki, 1953 (Morawiecki, , 1962)) , the white clay was thought to be composed of kaolinie relatively free of chemical and mineral contaminations apart from quartz; a microscopic study found only well crystallized anatase, mica and quartz. Recently this kaolin clay has been carefully examined by X-ray diffraction and rather unusual properties were discovered which cannot be attributed to a. normal kaolinite. The X-ray diffraction pattern of a fully disoriented aggregate (Fig. 1 ) does not resemble that of a pure kaolinite. It differs in the number of reflections, their relative intensities, and the exact angular positions of the basal reflections. Such a pattern might result from a mechanical mixture of metahalloysite and kaolinite rather than pure kaolinite (Brindley et al. 1963) . Electron micrographs, however, show a platy material (Fig. 2 ).