Occurrences and Mineralogical Properties of Long-fibrous Palygorskite from Guizhou Province, China

Abstract

Palygorskite is a hydrous magnesium and aluminum silicate classified as one of clay minerals. It has a structure similar to sepiolite, however, there is some vacant site in octahedral sheet caused by substitution of Mg ion by Al and Feions. Considerable amount of attapulgite, clayey variety of palygorskite, have hitherto been imported from U.S.A. and used as industrial raw material for adsorbent, filler, catalyst, and so on. Recently, occurrence of macroscopically long fibrous palygorskite in China become known, and several amount of this material has been imported tentatively. However, in so far as our knowledge, its mode of occurrence and the mineralogical properties have not been reported yet.
In this paper, mode of occurrence and the mineralogical properties of macroscopically long fibrous palygorskite from three deposits in Guizhou Province, China is reported. In these deposits, palygorskite has been formed as veins crossing limestone or calcareous mudstone of Permian or Triassic Period developed around the deposit. XRD study clarify that these minerals are well crystallized palygorskite. Calcite and quartz were frequently detected as impurity. In rare case fluorapatite is also found as impurity. In addition to these impurities, surface of the palygorskite vein is usually contaminated by brown clay come from earth surface through palygorskite veins. Mineralogical data such as TG-DTA curves, chemical composition, SEM and TEM photographs are presented.
The mode of occurrence as well as mineralogical properties of the palygorskite confirm that the palygorskite under consideration is supergene origin, and directly precipitated from meteoric water rich in magnesium, aluminum and silica with minor amount of iron.