 A. Calkins in their 1964 work on the Curlew Quadrangle of Ferry County.Since then the fossil-bearing strata of the Formation have been radiometrically dated, to give a current estimate of the Ypresian, the mid stage of the early Eocene.Parker and Calkins in 1964 noted the association of the Klondike Mountain Formation with the gold and silver deposits of the Republic District and suggested it as a potential host to more ore deposits in the Curlew Quadrangle.