R2: Crystal structure, crystal chemistry, physical properties of minerals, crystal growth and applied mineralogy

[R2P-05] Property and formation process of the overgrowth layer on quartz crystals

*Hiroaki Ohfuji¹, Watanabe Rino² (1. Tohoku Univ. Sci., 2. Ehime Univ. GRC)

Keywords:Quartz crystal, Overgrowth layer, Wavy extinction, Misorientation

We studied the characteristics and formation process of microcrystalline quartz covering the {100} planes of hydrothermal quartz crystals using natural samples with small and large degrees of the overgrowth. The result showed that the formation of microcrystalline quartz initiates with roughening of {100} surface as a result of rapid increase in supersaturation of the solution, followed by the elongated growth of quartz crystals toward [001] perpendicular to the {100} of the mother quartz crystal through geometric selection.