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by metamorphic agencies


Plate XXII (cropped)
A. Fine-grained green and white brecciated marble from Aslaka-Shamrock Marble Co's property, Dichman Bay
B. Fine-grained dark grayish-green and white brecciated marble ("Black and White"), from Alaska-Shamrock Marble Co.'s property, Dickman Bay.
illustrating Ernest F. Burchard. "Marble Resources of Southeastern Alaska, With a section on the geography and geology by Theodore Chapin." USGS Bulletin 682 (1920): 1-118
Stanford copy

The chief agents that bring about these changes are pressure, heat, and chemical action, generally at considerable depths below the surface of the earth. By metamorphic agencies limestone is transformed into marble.
p 18

5 January 2014
tags: E. F. Burchard; economic geology; marble; mental states; out of focus