Significance: In the past decade, sporadic shortages of metals and metalloids crucial to modern technology have inspired attempts to determine the relative “criticality” of various materials as a guide to materials scientists and product designers. The variety of methodologies that have been used for this purpose have (predictably) resulted in widely varying results, which are therefore of little use. In the present study, we develop a comprehensive, flexible, and transparent approach that we apply to 62 metals and metalloids. We find that the metals of most concern tend to be those with three characteristics: they are available largely or entirely as byproducts, they are used in small quantities for highly specialized applications, and they possess no effective substitutes.

Significance: Modern life is enabled by the use of materials in its technologies. Over time, these technologies have used a larger and more diverse array of materials. Elemental life cycle analyses yield an understanding of these materials, and a definite concern that arises is that of possible scarcity of some of the elements as their use increases. We studied substitution potential for 62 different metals in their major uses. For a dozen different metals, the potential substitutes for their major uses are either inadequate or appear not to exist at all. Further, for not 1 of the 62 metals are exemplary substitutes available for all major uses.

Metals that are obtained largely or entirely as by-products are essential to modern technology, but their supplies may be constrained due to a variety of factors.

Significance: Expanding demand for nonfuel minerals that enable pivotal technologies has elevated concerns regarding supply security, especially for nations that are highly import reliant. Although import reliance has become a prominent concern, few studies assess import reliance and none compare import reliance of countries concurrently. Doing so provides insights into resource interdependency and competition potential. Here, we compare the net import reliance of 42 minerals for the two largest national economies, China and the United States. We find that China relies on imports for over half of its consumption for 19 minerals, compared with 24 for the United States—11 of which are common to both. It is for these 11 minerals that competition between the United States and China may become the most contentious.