(AP) — A Canadian mining firm is preparing to resume drilling samples from beneath southeast Nebraska to determine if it will be feasible to build a mine to harvest a valuable and rare heat-resistant element.

NioCorp Developments said Tuesday it has requested bids from drilling companies for this summer’s exploration of the niobium deposit near Elk Creek.

NioCorp said last month it had raised $5.5 million to pay for this next phase of drilling and assessment.

The U.S. currently imports nearly all the niobium that’s used in this country to harden steel and make it more heat-resistant for industrial uses.

NioCorp previously estimated that more than 100 tons of niobium rests several hundred feet below the ground, but it’s not yet clear whether a mine will be built.

Elk Creek is about 45 miles east of Beatrice.