William Frank Bradley

Quantitative Estimations of Clay Minerals by Diffraction Methods

ABSTRACT The clay mineral components of Recent sediments and soil materials exhibit structural attributes unlike those of many so-called standard clay materials. The interpretation and significance of some of these is discussed in detail. Factors involved in analyzing these materials quantitatively are considered and a general procedure outlined.

The vaterite‐type ABO3 rare‐earth borates

Approximate models are proposed for the room temperature and the high temperature modifications of the vaterite-type rare earth borates. A low temperature model based on three-membered rings of borate tetrahedra is found to be reconcilable with the X-ray powder diffraction data, the optical properties, and the infrared absorption character. A high-temperature model containing triangular borate ions is relatable to the CaCO3 vaterite modification.

CLAY MINERAL COMPOSITION OF SOME SEDIMENTS FROM THE PACIFIC OCEAN OFF THE CALIFORNIA COAST AND THE GULF OF CALIFORNIA

This report presents the results of a study of the clay mineral composition of a series of bottom core samples collected by the staff of the Scripps Institute of Oceanography of the University of California in Pacific Ocean off the California coast and in the Gulf of California. The clay minerals were studied by X-ray diffraction, differential thermal, optical, chemical, and electron microscopic methods following particle size fractionation by sedimentation and supercentrifuge procedures. All of the samples from the Pacific Ocean and from the Gulf of California contained illite, montmorillonite, and kaolinite; generally illite was most abundant and kaolinite least abundant. A chloritic clay mineral could be identified definitely in some samples. The clay minerals were in very complex mixtures, including mixed crystallizations as well as mechanical mixtures of discrete phases. In general the crystallinity was lower, the individual size smaller, and the intergrowth more intimate than in ancient sediments which have been studied by the authors. Small amounts of quartz were associated with the clay minerals in the 1 to 0.1 and minus 0.1 micron fractions. Small amounts of another nonclay mineral crystalline phase that is probably a feldspar were also found in the finest size fractions of many samples. The analytical data suggest that kaolinite is slowly lost during diagenesis under marine conditions, perhaps being changed to an illite or chloritic clay mineral. The data also afford evidence that potash is taken up by the clay and suggest that it is taken up largely by partially degraded illite which is carried into the sea. Magnesium also appears to be taken up by the clay, perhaps by the illite. The widespread occurrence of montmorillonite indicates that this clay mineral is not lost quickly if at all during diagenesis under marine conditions.

Current Progress in Silicate Structures

Attention is called to the value to be derived from application of diffraction analysis of modern grade to specific, familiar, approximately known crystallizations. Features consequent to ordering of coordination polyhedra of differing sizes in layer structures are discussed, and their bearing upon relations between lattice parameters and chemical compositions are outlined.

A Discussion of the Water Content of Vermiculite

Selected chemical and diffraction analyses from the literature, supplemented by thermal and thermogravimetric analyses and infrared absorption observations, are utilized to construct a rational model of the water arrangement in natural vermiculites.

Structural Irregularities in Hydrous Magnesium Silicates

The crystal structures of chrysotile, antigorite, attapulgite, sepiolite, vermiculite, and montmorillonite are discussed in the light of the degree to which they resemble chlorite.