Extraordinary Crystals of Natural Minerals in Mining Sites and Volcanoes

Many mineral crystals in natural environments exhibit unique morphologyMorphology, size, color, microtexture, and other properties that have not yet been reproduced artificially, and the understanding of their formation mechanisms may provide insights for the development of new crystalline materials. This review introduces two specific examples of such natural minerals: karpatite, natural crystal of coroneneCoronene in hydrothermal metal deposits and Al/Si disordered anorthite, metastable aluminosilicate mineral in volcanic rocks. The former mineral shows distinctive fluorescent property which is different from the artificial crystal of coroneneCoronene and the latter mineral is characterized by very large size (>1 cm single crystal) despite its metastability. Their occurrences are "out of the ordinary" because they cannot be explained by simple crystal growthCrystal growth such as cooling or fractionation. However, careful observation and analysis of those natural minerals provide a reasonable explanation for the formation of extraordinary crystals in natural environments. It is expected that the knowledge obtained from such natural minerals will be applied to the crystal engineering for developing functional crystalline materials.