Wow this has been a long strike. This is a subscription site but there is enough here to tell us what is going on and this is something myself and fxstc have followed for months.

July 6, 2020, 3:38 PM

2,000 miners will return to work after 9 months
NLRB denies representation challenge

Nearly 2,000 workers for the ASARCO mining company ended a nine-month strike Monday, citing a recent National Labor Relations Board action against their employer.

The United Steelworkers union said ASARCO employees in Arizona and New Mexico would return to work after the NLRB determined it would prosecute the company for alleged unfair labor practices. The workers had been on strike since October, arguing that the Arizona-based company, a subsidiary of Mexican mining corporation Grupo México, was negotiating in bad faith over a new four-year contract.

And I just found another source that is not subscription:

Unions Offer to Return to Work at ASARCO, End Nine-Month Strike

PITTSBURGH, July 6, 2020 /PRNewswire/ -- The United Steelworkers (USW) today said that the unions representing almost 2,000 workers on strike against ASARCO's unfair labor practices at five copper mining and processing facilities in Arizona and Texas have ended the labor dispute and offered to return to work.

"In light of the National Labor Relations Board's (NLRB) decision to prosecute ASARCO for alleged violations of federal labor laws," said USW District 12 Director Gaylan Prescott, "the best strategy for the most bargaining leverage is to end the current strike and make an unconditional offer to return to work."

"The USW, other unions and the NLRB are bringing ASARCO to justice for breaking the law in its drive to avoid negotiating in good faith with the unions that represent its employees," Prescott said. "Now is the time for management to bargain for the fair contract workers have earned and deserve."