Abstract
A critical review is given of how the knowledge on the morphology of mineral crystals can be practically used to understand the kinetic processes in natural crystallization. Based on the analysis of R-σ relation in relation to the morphology of crystals, the characteristics of crystal growth taking place in magma are analysed. Dendritic and hopper crystals can appear only when a magma is solidified under extreme conditions, and the most rock-forming crystals grow by layer-by-layer growth mechanisms to form bulky crystals. Significance of internal heterogeneities in these bulky crystals, like lineage structures, growth bandings and sector structures is explained in relation to geological problems. Crystal growth mechanism taking place in hydrothermal metasomatism, contact and regional metamorphisms are analyzed based on the observations of the surface microtopographs of crystals. In hydrothermal metasomatism and contact metamorphism, it is assumed that the original solid rocks are dissolved to form a new low supersaturated solution from which crystals grow by the spiral mechanism. In contrast, crystallization in regional metamorphism is best simulated to the sintering process, in which Oswald ripening occurs extensively. Habit changes of bulky crystals grown in hydrothermal solutions are explained in relation to their growth environments, using calcite and pyrite as examples. Origin of striated faces is put forward as a problem to be solved in future.
