If you have access to the most recent April Buyer's Guide issue of the Lapidary Journal magazine, scan its lists of gem and mineral clubs in the United States and other countries. Talk to a member of the geology or earth science department of your local college or university. Talk to a member of the science department of your local high school. The USGS reports deposits that seem likely to contain gemstones. It is not a function of the USGS to exploit such resources.
USGS geologists perform continuing research on kimberlites, the initial source of diamonds.
Not all kimberlites are diamond bearing, and some of the research is directed to learning what indications you look for during exploration to distinguish fertile from barren kimberlite. USGS geologists are compiling a U.S. map showing the locations of known kimberlites.