The Coeur d'Alene (Silver Valley) Mining District is located in Proterozoic metasediments. The mined portion of the stratigraphic column in the Silver Valley, known as the Belt series, can be divided into six main formations, three of which have upper and lower parts. These are, from oldest to youngest: the Prichard Formation (lower and upper), Burke Formation, Revett Formation, St. Regis Formation (lower and upper), Wallace Formation (lower and upper), and Striped Peak Formation. Of these, all but the Striped Peak are ore-bearing. All six of these formations are primarily composed of quartzite and argillite. Some limestone and dolomite also occur in the Wallace and Prichard, and a smaller amount of carbonate occurs in the St. Regis. Ripple marks and mud cracks occur throughout the series. Together, these imply a shallow marine depositional environment.