The U.S. stock market plunged by the widest margin in six months on Friday, with the S&P 500 shedding nearly 3% after President Donald Trump threatened “a massive increase of tariffs on Chinese products” due to its continuing strict control of the rare earths market. On Thursday, Beijing announced that it was increasing export controls for five more rare-earth metals, bringing the total number of critical minerals under export control to 12. Under the previous restrictions, Beijing required exporters to ap ...