Clay mineralogy of Turkish borate deposits

Abstract

Turkish borate deposits, which are considered the largest in the world, have been studied for their clay-fraction mineralogy, the chemistry and the physico-chemistry of their depositional environment. It is found that, in most cases, Mg-montmorillonite, hectorite, vermiculite and mixed layers of 14 M–14 C, 14 M–14 V and 14 V–14 C are the dominant minerals in these deposits with Mg 2+ being the principal ion of octahedral sites and K + being the principal exchangeable ion in phyllosilicates, where Sr 2+, Ca 2+ and Li + appear to be the minor constituents. Na + and Ca 2+ occur in borate minerals as co-genetic with the clay minerals. It is also found that these deposits contain fifteen different varieties of borate minerals. It is suggested that borate, carbonate and an important part of phyllosilicate minerals were authigenically formed in a relatively warm lacustrine environment with a pH around 9. One of the most interesting aspects of the samples studied from these deposits, is the existence of amorphous fractions of siliceous composition.