A Structural Study of Talc and Talc‐Tremolite Relations

About forty specimens of talc have been examined by X‐ray powder methods. Variations in the degree of crystallinity of the mineral have been observed, but no evidence has been obtained for polymorphic structural varieties. Single‐crystal data have confirmed the two‐layer mono‐clinic cell. Little evidence has been obtained of talcs containing mixed‐layer sequences. Electron micrographs have revealed a variety of platy and fibrous forms, and in the latter a close structural relation between talc and tremolite has been established. Talcs prepared synthetically in the presence of aluminum showed small lattice parameter differences from talcs prepared in the absence of aluminum, and the results are consistent with the substitution of small percentages of A1 ions in the talc structure. New X‐ray powder data and unit‐cell parameters for talc and tremolite are listed.