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Pegmatites--Black Hills (S.D. and Wyo.)


Quantitative microscopic and chemical anaylses of 12 specimens of microcline, most of them perthitic, from the zoned Hugo pegmatite in the Black Hills near Keystone, South Dakota, have yielded data that can be used to estimate the temperatures of crystallization at successive stages in the formation of the pegmatite. The determined temperatures of crystallization range from 565°C in zone 3a, near the margin of the pegmatite, to 280°C in zone 7, the core.

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