Reliable access to critical minerals is a matter of both economic and geostrategic importance to the United States. Indeed, concern about access to minerals is rising now due to increasing demand, new competitors capturing large market shares and other trends that defy easy prediction. These same trends can interfere with important foreign and defense policy goals and give mineral suppliers easy leverage over the United States. This report explores a range of potential vulnerabilities that stem from dependence on several minerals that the United States will need for defense supply chains and clean energy goals in the decades ahead. The report examines cases of five individual minerals -- lithium, gallium, rhenium, tantalum and niobium -- and rare earth elements, such as neodymium, samarium and dysprosium, as a sixth group in order to show the complexity of addressing these concerns. As the report recommends, the U.S. government can take several cost-effective, proactive measures to prevent mineral issues from impinging on security, foreign policy and economic growth plans in the years ahead.