An interactive graphic shows where supplies are concentrated.

By Nicolas Rapp and Brian O'Keefe
June 29, 2017

Nothing can stop the proliferation of iPhones, solar panels, and Teslas—except, perhaps, a shortage of key natural resources. The prices of “technology minerals” such as cobalt (recently up 76% year-to-date) and lithium (up 21%), crucial to ­making, say, batteries for electric cars, have spiked recently. It’s a trend that bears watching for companies such as Apple aapl and Tesla tsla . And it could be just the beginning. In March, an international team of researchers, led by Saleem Ali, a professor of energy and the environment at the University of Delaware, published a peer-reviewed paper in the journal Nature warning of possible shortfalls in supply of important commodities. The researchers looked at projected demand for these technology minerals and concluded that much more investment in exploration is needed for supplies to keep up. Adding to the challenge for Silicon Valley: Deposits of these minerals are largely ­concentrated outside the United States. Click on the graphic below to see which countries were the largest exporters of the resources to the U.S. last year.

A version of this article appears in the July 1, 2017 issue of Fortune with the headline “Most Wanted Minerals.”

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