SYNTHETIC Mg-CHLORITE IN RELATION TO NATURAL CHLORITE

抄録

X-ray and infrared studies have been made on synthetic materials prepared hydrothermally at 300-660°C and 18, 000-38, 000 psi from gels with compositions ranging from pennine to amesite. The results indicate that the solid solution range of the chlorite phase does not extend to the amesite composition in the present experimental conditions; the range is almost identical or slightly extended to the Al-rich side compared with that of natural well-crystallized Mg-chlorites. The polytype of the synthetic Mg-chlorite is IIb, which exhibits regular stacking in the high aluminum materials. The differences in cell dimensions and OH bands between the synthetic and natural chlorites suggest a difference in the distribution of cations within the talc and brucite octahedral layers. An even distribution of the octahedral cations is inferred for the synthetic chlorite, which is regarded as a high temperature form. The latter conclusion is supported by a hydrothermal treatment of natural chlorite. Additional information on the polytypes of the serpentine phase is also presented.