There are more than 42,000 entries in the USGS Mineral Resources Data System (MRDS) for the State of California. Previously, the field for deposit type was sparsely populated, which made it difficult to evaluate mine sites needing environmental remediation. This has been rectified by populating the deposit type field using 100 deposit types cited in previous USGS publications, and 137 provisional deposit types described here. Other categories listed in the deposit type field include 29 types of mineral processing facilities, 6 miscellaneous categories used previously in MRDS, and 56 unclassified categories tied to primary commodity. References are provided for each deposit type, as available, including descriptive models, grade-tonnage models, and geo-environmental models. The new information on deposit type will be useful to federal, state, and local agencies concerned with prioritizing abandoned mine sites for environmental assessment.