This data release provides descriptions of more than 60 mineral regions, mines, and mineral deposits within the United States and its territories that are reported to contain enrichments of cobalt (Co). To focus the scope of this data release, we report only mined deposits and exploration prospects with past production, or resource and reserve estimates of 1,000 metric tons or more of cobalt. Cobalt has diverse uses because of its properties, which include ferromagnetism, hardness, wear-resistance, low conductivity, and high melting point. The primary uses for cobalt are in rechargeable battery electrodes, and in superalloys used to make gas turbine engines. In 2017, the United States had a net import reliance as a percentage of apparent consumption of 72 percent for cobalt, and cobalt is considered a critical mineral. Cobalt mineralogy is diverse; it occurs in a variety of sulfide, arsenide, sulfarsenide, and oxyhydroxide minerals. In the United States, cobalt could be derived as a byproduct from mineral deposits that primarily produce other metals, including nickel, copper, zinc, and lead. The inclusion of a particular mineral deposit or prospect in this database is not meant to imply that it has economic potential. Rather, these entries were included to capture the characteristics of the deposits and prospects in the United States and its territories that have the largest cobalt resources. These deposits and prospects occur in Alaska, California, Idaho, Maine, Michigan, Minnesota, Missouri, Montana, North Carolina, New Mexico, Oregon, Pennsylvania, Puerto Rico and Tennessee. Several deposits and prospects were not included in this database, because they contain less than 1,000 metric tons of cobalt. A prime example is the Bunkerville project in Nevada (Ludington and others, 2006).
The Stillwater deposit in Montana produced cobalt, but this was a byproduct, and to our knowledge, there are no published records of the amount of cobalt produced, or the amount of cobalt contained within the deposit. Analyses of rock chips from 47 outcrops of the Katahdin deposit in Maine indicates that the deposit locally contains approximately 0.1 percent cobalt (Miller, 1945), but a thorough analysis of the deposit is lacking.
Mine La Motte in Missouri and the Stone Corral project in California were not included because of a lack of ore reserve information in publicly available references. However, we are aware that cobalt is present in the area and we welcome further information on these sites. The entries and descriptions in the database were derived from published papers, reports, data, and internet documents, published from 1908 to 2018, representing a variety of sources, including geologic and exploration studies described in State, Federal, and industry reports. Although an attempt was made to capture as many examples as possible, this dataset is a progress report that is part of an ongoing effort. The authors welcome additional published information in order to continually update and refine this dataset.