CLINOPTILOLITE IN SOUTH TEXAS SOILS

Clinoptilolite, Ca//x(Na,K)//6// minus //2//x left brace Al//6Si//3//0O//7//2 right brace multiplied by (times) 24H//2O, frequently has been recognized in Cenozoic volcanogenic sedimentary rocks; however, its occurrence in soils has received little attention. In the course of this study, clinoptilolite was identified in calcareous soils derived from volcanic-rich sediments of the Catahoula Formation in south Texas. The mineralogical properties of clinoptilolite were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), electron microprobe analysis, and analysis of exchangeable cations. About 2 to 5% clinoptilolite by weight was found in the A and B horizons and concentrations progressively increased with depth to as high as 20% in the C horizons. No differences in the zeolite structural framework or Si/Al atomic ratio were detected throughout the soil profiles examined.