It was restarted a few years ago in reaction to the possibility of the Chinese controlling a core of the defense supply chain, but again got undercut and the company that owns it is in bankruptcy.
In addition, unlike our environmental standards which in California don't allow for that type of mining at all, in China there is no environmental standards, and lots of people, and already control of 95% of the market so its easy to pull strings as an underdog tries to gain market when you can pull enough strings and control prices that much.
Additionally production is much cheaper when labor is cheaper and there are no environmental restrictions whic modulate production.
it is very easy for them to undercut and it will continue to be so as long as we don't allow internal mining and buy it elsewhere because there is a pervading belief or cognitive dissonance surrounding the idea that pollution produced in China doesnt effect pollution in California, and by exporting the manufactoring of goods bought in California to China with less restrictions, we are improving the state of the world.