From introduction: The purpose of this paper is to describe the geology and mineral resources of a part of the Copper River Basin between the Richardson Highway and the valley of the Klutina River, together with small areas east of the highway and west of the river. For convenience in reference this area is called the Tonsina district, as the Tonsina River and Tonsina Lake are conspicuous local geographic features, and the Tonsina Road House, on the highway at the crossing of the river, is one of the oldest and best-known settlements in the Copper River Basin.