Details
ColorsGrey
Origin
Description
An intriguing set of four rare Andesine Feldspar crystals contained in a small glass phial from Sinano, Japan. Andesine is a variety of Albite, originally described from Marmato mine, at Marmato in the Chocó Department of Colombia. mindat sates Andesine is "a plagioclase feldspar with an albite : anorthite molar ratio ranging from 50 : 50 to 70 : 30." There appear few references to this occurrence in Japan, although one can be found in a paper titled "On the Feldspar Crystals from Bunkeimen, Korea" by Masawo Isibasi from the Department of Geology and Mineralogy, Faculty of Science, Hokkaido Imperial University, No. 249. the paper describes the granitic region of Ryuenri, Bunkeimen, Bunkeigun, Keisyohokudo, Tyosen (Korea) and states "Our feldspar crystals may be recognised as cyclic-eightlings, repeating Baveno-twin and Parallel-growth with reference to each other. A similar twin crystal of feldspar has been found in Sinano in Japan, and according to C. Iwasaki, it was described as a quadruple twin-crystal of the Baveno and Manebach type.". This specimen is currently in Tucson as I make this description, so I can only go by the photo. Judging from information on the internet, these are not common Feldspar crystals and hence the reason this phial was prepared. It comes with an old hand written label.
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Origin
