Published: May 31, 2016 10:02 a.m. ET

Shares of Cliffs Natural Resources Inc. CLF, +36.32% rocketed 36% in active morning trade Tuesday, enough to make them the biggest percentage gainers listed on the NYSE, after the mining company announced a new 10-year commercial agreement to supply Arcelor Mittal USA LLC MT, +4.24% with iron ore pellets. Trading volume reached 18 million shares within the first half hour of trade, compared with the full-day average of 12.5 million shares, according to FactSet. Cliffs said the new agreement establishes a minimum tonnage of pellets of seven million long tons, which is higher than the combined minimum levels of the agreements that expire in December 2016 and January 2017. The stock has nearly tripled year to date, while the S&P 500 has gained 2.8%.