Study on the physical properties and genesis of borate minerals in skarns.

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The present study aims at claryfing the physical properties and genesis of borate minerals in skarns, which are formed as high-temperature metasomatic products at Fuka, Okayama Prefecture.1. Occurrence of borate minerals : Skarn minerals such as gehlenite and spurrite were primarily formed as high-temperature metasomatic products. During the post-metassomatic stage, the skarns were cut by numerous veins which consist of hydrated calcium silicates, fluoline-bearing minerals, and boron-bearing minerals. A vein consisting of borate minerals developed along the boundary between crystalline limestone and the skarns. The vein was approximately 10 cm in thickness, although in one part expanded to 3m. At the center of the expanded area, takedaite occurred. At the circumference of the expanded area, hydrous borates such as olshankyite, frolovite, sibirskite, borcarite and parasibirskite occurred 20 cm to 50 cm in thickness.2. physical properties of borate minerals : The mineralogical propertes such as optical properties, hardness, density, X-ray diffraction properties, chemical composition, thermal properties and Infrared absorption spectrum of many borate mineals, were revealed through this study.3. Genesis of borate minerals : From the mode of occurrence, the data on the sulphide minerals and the data reported by Schafer (1968), the formation of these minerals may be considered as follows : (1) takedaite was formed by reaction of boron-bearing fluids with limestone ; (2) sibirskite and parasibirskite were formed by hydrothermal alteration of takedaite ; (3) the late-hydrothemal solution converted sibirskite and parasibirskite to olshanskyite, frolovite, etc.