Asymmetry of growth and dissolution on basal, minor rhombohedral and prism faces of quartz

Hydrothermal method of temperature difference was employed to determine relationship between growth and dissolution rates on the basal, minor rhombohedral and prism faces of quartz at the same absolute values of the temperature gradient, |Δ T|, and correspondingly the same absolute values of super- and undersaturations, |Δ C|. The experiments were carried out in 1 m NaOH solution pre-saturated with silica at 1 kbar and (a) 300, 320, 340, 350, 360 °C and |Δ T|=10 °C; (b) 350 °C and |Δ T|=10, 15, 20 °C. It was found, that the ratio between absolute values of dissolution and growth rates increased from ∼0.9 to 9.0 on the following quartz faces: basal kinked face of maximum growth rate; minor rhombohedral flat face, having small area and intermediate growth rate; and prism flat face of maximum area and minimum growth rate, thus reflecting enhancement of growth and dissolving asymmetry (the weakest on the kinked face and the highest on the flat one, of maximal area).