1. Maps showing gravity and aeromagnetic anomalies in the Butte 1⁰ x 2⁰ quadrangle, Montana Yale Public content 1994. 2002-06-01T04:00:00Z. 2002-06-01T04:00:00Z. Geological Survey (U.S.). The Survey ; For sale by Map Distribution. English. Public. Montana and Butte Region.