Montana (Missouri River, NE of Helena, also Yogo Gulch, near Utica); discovered 1865, 1895. Also from Rock Creek in Granite Co.. Early and continued sources of much industrial-grade material. Also the source of considerable gem material (about $25 million from Yogo Gulch from 1895-1929).
Gold and sapphires in Missouri river gravels mined intermittently from 1865-present. Sapphires usually quite small, well-rounded or flat, and of a pale blue or blue-green color.