MINERALOGY OF THE SWELL-SHRINK SOILS OF THE STAVROPOL REGION

Analysis of 196 samples has shown that the mineral content of the clay in the Solonchakic and deeply Solochakic soils of the Stavropol regio n includes a smectitic phase (20-50 percent), dioctahedral hydrous mic a (11-50 percent), kaolinite (12-26 percent), chlorite (10-22 percent) , and finely dispersed quartz. The smectitic phase consists mainly of complex unordered mixed-layer formations of several kinds, including a predominance of smectitic mica with a high content of smectitic packe ts, as well as individual smectite usually in the lower horizons. The composition of the smectite packets is discussed in detail on the basi s of K and Li tests.