WINNEMUCCA, Nev. (AP) — Hycroft Mining Holding Corp. shares rocketed higher in midday trading Wednesday, fueled by fresh data showing substantial growth in its massive precious metals deposit.

The company filed an updated independent Technical Report Summary that pegs measured and indicated resources at 16.4 million ounces of gold and 562.6 million ounces of silver, up 55% from prior estimates, Hycroft said in a statement. Officials also disclosed an initial high-grade silver resource of 90.2 million ounces in the same categories.

“This updated Mineral Resource Estimate reflects significant growth in what is already among the world’s largest precious metals deposits,” President and CEO Diane Garrett said in the release. She highlighted drilling over the past 14 months that uncovered two new high-grade silver systems at Brimstone and Vortex, both open along strike and at depth with underground mining potential.

Metallurgical tests bolstered the news. Pressure oxidation processing yielded 83% gold recovery and 78% silver recovery. Flotation tests hit 89.5% for gold and 92.9% for silver, with pressure oxidation reaching 93.5% gold and 86% silver recovery, according to the report.

Hycroft is testing a roasting process that could generate sulfuric acid as a byproduct, opening a potential third revenue stream, company executives noted.

Shares of HYMC climbed 15.15% to $3.87 by early afternoon, according to Nasdaq data. The stock has swung wildly in recent months amid volatile gold and silver prices and investor bets on refractory ore breakthroughs at the company’s namesake mine northwest of Winnemucca.

Hycroft’s deposit ranks among the largest undeveloped gold-silver assets in North America. The latest resource update follows a 2023 pit optimization study and ongoing efforts to improve recovery from double-refractory sulfide ore, which resists traditional cyanide leaching.

Garrett, who took the helm in 2021, has pushed aggressive exploration since high-grade silver intercepts emerged last year. “We’ve established continuity in these systems much faster than anticipated,” she added.

Analysts tracking the stock pointed to the resource expansion as a key de-risking step. The updated figures incorporate 2024 drilling data and refined geologic modeling, the Technical Report states. Hycroft plans further work to convert inferred resources and advance permitting for potential production restarts.

The mine last produced commercially in 2021 before suspending operations amid high costs and low metal prices. Current efforts focus on heap leach expansions and sulfide processing viability.

Gold traded at $2,650 per ounce and silver at $31 Wednesday, supporting mining stocks across the board. HYMC outperformed peers, with volume exceeding 5 million shares by 1 p.m. ET.

Company officials did not immediately respond to requests for additional comment.