Stress-Induced Lattice Imperfections: the Principal Motive in Enhancing some Physico-Chemical and Electrical Properties of some Quartz Varieties

Abstract

Chemical reactivity, grindability and zeta potential have been measured and correlated for three variably deformed quartz varieties from three different areas. Results show that there is a strong positive correlation between lattice imperfections and the measured physico-chemical and electrical properties of the three varieties. The highly deformed blue-grey quartz variety records the highest dissolution, grindability and surface electric charges compared to the less deformed milky and rose varieties. Microfabric study supported with XRD results show that the shear-related blue-grey variety exhibits a very strong intracrystalline deformation and high dislocation density indicative of low to intermediate grade conditions. The other two varieties, on the other hand, exhibit deformation features and lower dislocation densities pointing to a much lower grade. The higher chemical reactivity of the blue-grey quartz can be attributed in part to the morphological modifications the shearing creates within the quartz tetrahedra, and to the piezoelectric effect. Such modifications facilitate breaking the Si–O bonds, and lower the activation energy required to initiate the reaction between the silicon ions and the hydroxyl group. Piezoelectricity increases the electric potential across the crystal-liquid interface and hence setting the stage for the chemical reactions. The doubled value of zeta potential of the blue-grey quartz relative to the other two varieties opens the discussion of whether the inherited paleo-piezoelectricity of deformed quartz may enhance and play a significant role in the process of quartz dissolution or not.