The American Gem Mining Syndicate was a Philipsburg, Montana, sapphire mining company. Records include interoffice correspondence (1903-1935), general correspondence (1902-1929), court papers (1906-1915), employment records (1912-1930), financial records (1904-1930), legal documents (1903-1907), organizational records (1901), and production records (1911-1914). [Maps were transferred to Library Map Catalog].

This collection consists of views of Montana placer mining, hard rock mines and mills, coal mines, and kilns primarily between the years 1867 – 1920. Well-represented are early views of placer mining in Alder Gulch and in the Rimini mining district, larger-scale hard rock mining in the Marysville mining district, and mines and smelters in Butte. The collection also includes views of coal mining operations in Carbon, Fergus, Gallatin, Park, Powder River, and Sheridan counties.