Abstract
Five new chemical analyses and X-ray studies of the kaolinite-like clays of the lone Formation, near lone, California give the correct kaolinite chemical formula with Si:(Al+Fe+Ti) ratios of 0.985, 1.012, and 0.995. X-ray powder patterns indicate partially disordered kaolinites.
A new chemical analysis of a sample from the sandstone of the lone Formation of the Mokelumne River, California, confirms older analyses with high Si:(Al+Fe-(+Ti) ratios not compatible with the theoretical kaolinite formula. Treatment of this material with sodium hydroxide reduced the Si:(Al+Fe+Ti) ratio to 1.000. X-ray powder photographs before and after leaching with NaOH are identical and typical of disordered or partially disordered kaolinites. The excess silica is probably in the form of amorphous colloidal silica and may have been deposited within the kaolinite platelets after their deposition.
