To define and prioritize focus areas across the United States with resource potential for 35 critical minerals in a few years' time, the U.S Geological Survey Earth Mapping Resources Initiative (Earth MRI) required an efficient approach to streamline workflow. A mineral systems approach based on current understanding of how ore deposits that contain critical minerals form and relate to broader geologic frameworks and the tectonic history of the Earth was used to satisfy this Earth MRI need. This report describes the rationale for, and structure of, a table developed for Earth MRI that relates critical minerals and principal commodities to the deposit types and mineral systems in which they are concentrated. The hierarchical relationship between systems, deposits, commodities, and critical minerals makes it possible to define and prioritize each system-based focus area once for all of the critical minerals that it may contain. This approach is advantageous because mineral systems are much larger than individual ore deposits and they generally have geologic features that can be "imaged" by the topographic, geologic, geochemical, and geophysical mapping techniques deployed by Earth MRI.

of critical minerals in coordination with the Bureau of Land Management. In response, a list of 35 critical minerals was compiled using a quantitative screening tool (Fortier and others, 2018). The draft list of 35 minerals or mineral material groups deemed critical was published in May 2018 by the Federal Register (Federal Register, 2018). A "critical mineral," as defined by Executive Order 13817, is a mineral (1) identified to be a nonfuel mineral or mineral material essential to the economic and national security of the United States; (2) from a supply chain that is vulnerable to disruption; and (3) that serves an essential function in the manufacturing of a product, the absence of which would have substantial consequences for the U.S. economy or national security. Disruptions in supply chains may arise for any number of reasons, including natural disasters, labor strife, trade disputes, resource nationalism, and (or) conflict. To address the new data needs in order to develop an inventory of the regions that are known to be, or may be, prospective for increasing the domestic supply of critical minerals, the U.S. Geological Survey developed the Earth Mapping Resources Initiative. The initiative forms a partnership among the U.S. Geological Survey, State Geological Surveys, and private industries to identify focus areas for new digital data acquisition to increase the understanding of where critical minerals may be prospective. The outcome of the effort is to enhance the understanding of the United States' prospectivity for knowing domestic mineral supply to help decrease our reliance on foreign sources of minerals fundamental to the Nation's security and economy.

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A challenge for the global economy is to meet the growing demand for commodities used in today's advanced technologies. Critical minerals are commodities (for example, elements, compounds, minerals) deemed vital to the economic and national security of individual countries that are vulnerable to supply disruption. The national geological agencies of Australia, Canada, and the United States recently joined forces to advance understanding and foster development of critical mineral resources in their respective countries through the Critical Minerals Mapping Initiative (CMMI). An initial goal of the CMMI is to fill the knowledge gap on the abundance of critical minerals in ores. To do this, the CMMI compiled modern multielement geochemical data generated by each agency on ore samples collected from historical and active mines and prospects from around the world. To identify relationships between critical minerals, deposit types, deposit environments, and mineral systems, a unified deposit classification scheme was needed. This report describes the scheme developed by the CMMI to classify the initial release of geochemical data. In 2021, the resulting database-along with basic query, statistical analysis, and display tools-will be served to the public through a web-based portal managed by Geoscience Australia. The database will enable users to trace critical minerals through mineral systems and identify individual deposits or deposit types that are potential sources of critical minerals.

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