John C. Duncan has resigned from Fluor...

John C. Duncan has resigned from Fluor Corp.’s board to become chairman of Cyprus Minerals Co., the company that will own and operate the metals and coal assets spun off by Amoco Corp., the old Standard Oil Co. of Indiana.

Duncan’s resignation from Fluor’s board, which is effective immediately, was necessary because of the similar business interests of Cypress and Fluor’s St. Joe Minerals unit, a Fluor spokesman said.

Duncan, 64, came to Fluor when the Irvine engineering and construction giant acquired St. Joe in 1981. At the time of the acquisition, Duncan was chairman and chief executive of the Clayton, Mo., mining company, a position he continued to hold until retiring in December, 1982.