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Electron microscope studies of chrysotile show that tubes are present in bulk specimens and that these tubes commonly have fuzzy, amorphous-looking material on both the inside and outside. Similar material is associated with synthetic chrysotile and has been noted previously in halloysite specimens. The existence of such material between and within the tubes, together with apparent irregularities in size, shape and packing of tubes, explains the apparent discrepancy between the measured density of bulk samples and the calculated density of a hypothetical sample consisting of close-packed, regular, hollow capillaries. Replicas of fractured surfaces of halloysite (2H20) fl'om various localities reveal that the particles occur as curved to flat laths commonly possessing " hexagonal " terminations and surface features indicative of a higher degree of crystallinity than tubes of halloysite (4I~20). It is suggested that a complete morphological series from plates through laths to tubes exists both in platy to fibrous serpentine and in kaolinite to halloysite (4H~O). In each series a number of structural varieties are to be expected between the morphologically distinct " end members."

Improvements in replica techniques have made possible the high magnification study of textural characteristics and surface features of clay aggregrates found either in nature or in the laboratory. The most successful method of sample preparation involves pre-shadowing the specimen with platinum and backing this with a layer of carbon prior to removal of the clay with a suitable solvent.Data on orientation and packing of clay particles are readily obtained. The method is useful to investigate clays in which the characteristic morphology is easily affected by environmental conditions or by sample preparation for other methods of study.Replicas of kaolinite indicate that many of the pseudohexagonal plates seen in electron micrographs are cleavage fragments. Investigations of halloysite (4 H~O) using this technique prove that the tubes exist as such in the bulk clay. Striations on montmorillonite flakes that intersect at an angle of sixty degrees suggest a degree of morphological crystallinity that is apparently destroyed when the material is dispersed prior to study in the electron microscope. Replicas of dickite, attapulgite and weathered feldspar also show features that have not heretofore been seen in electron micrographs.

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