SHORT COMMUNICATIONS

Hydroxyl-stretching frequencies of serpentine minerals IN this study factors affecting the hydroxyl-stretching modes of some serpentines are investigated. Previously (Yariv and Heller-Kallai, I975) the relationship between some features of the 400 to I4oo cm-1 region of the spectra of these minerals and their structures was discussed. ~5 Fig. I shows the 32oo to 4ooo cm-1 region of spectra of representative samples that had been heated above 3o0 ~ Table I lists the observed frequencies and the ionic compo-sition of the samples studied. This was calculated from chemical analyses on the basis of O10(OH)s per formula unit. When analyses were carried out on the microprobe only total iron could be determined. z Samples were examined in the form of KBr, KC1, NaC1, and CsC1 discs of various concentrations, using a Perkin-Elmer 237 grating instru-ment. The samples were heated over-night at a range of temperatures up to 620 ~ and cooled in a desiccator. Some of the samples were also heated at 2oo ~ under vacuum. The spectra obtained were independent of the alkali halide used. Discs heated in air 4ooo to temperatures below 3oo ~ con-tained adsorbed moisture, but above this temperature the spectra were identical with those of corresponding MICRON