By editor
Rock Creek, Granite County
Near Philipsburg, the geology tells a different story of corundum. The Rock Creek sapphire deposit is alluvial. The original metamorphic host rock weathered away millions of years ago, and the heavy sapphires washed into the gravels of the local streams. Between 1890 and the 1930s, over sixty-five tonnes of rough sapphire were pulled from these hills to supply the watchmaking industry in Switzerland.
Visitor Access
Gem Mountain is a private, commercial fee-dig operation open from late May to early September. For roughly thirty-five to fifty dollars a bucket, visitors are provided with equipment and staff guidance to wash and screen the sapphire-bearing gravel. Unlike the uniform blue of Yogo Gulch, the Rock Creek sapphires come in a riot of colors. The operation also offers heat treating and faceting services for the stones you find.