The Basin Mining Company was a Granite County, Montana, gold mining company, with head offices in St. Louis, Missouri. Records include interoffice correspondence (1903-1923), general correspondence (1903-1925), records of a court case (1907), minor financial records, organizational records (1906-1922), and miscellany.

Paul Fusz was a Philipsburg, Montana, mining investor and businessman. Papers (1903-1912) include correspondence, court papers, legal documents, and reports relating to various mining ventures, including the Granite-Bimetallic Consolidated Mining Company. There are subgroups for the Rimini Mining Syndicate and the United Confederate Veterans.

The Royal Mining Company, originally the Royal Gold and Silver Mining Company, was located near Philipsburg, Montana. Records include correspondence (1899-1921) between company secretary W.M. Bickford and various stockholders and officers; assay reports; financial records; mining leases (1910-1921); and organizational records (1891-1912).

The Trout Mining Company produced manganese oxide for batteries. Records consist of scattered correspondence (1939-1951); payroll records (1956-1959), orders for equipment and supplies (1946-1953); production records, including a sample book (1958) for the Blaine Mine; reports; and miscellany, including field survey books (1936-1938).