Geologist Matt Joeckel displays a core sample of carbonatite rock containing niobium and rare-earth elements, which was taken from a deposit near Elk Creek, Neb., in early February. (Associated Press)
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Geologist Matt Joeckel displays a core sample of carbonatite rock containing niobium and rare-earth elements, which was taken from a deposit near Elk Creek, Neb., in early February. (Associated Press)
