Pg. 740-750. Butte granite or Butte quartz monzonite. Covers area of several sq mi and is prevailing rock of Butte district, [Silver Bow County], central western Montana, and the one that contains the world-famous copper and silver veins of that place. It is rather dark colored, coarsely granular rock. Age is Tertiary(?) (Eocene?).
Source: US geologic names lexicon (USGS Bull. 896, p. 305).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
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