Time to dig into why this rare-earth-mining stock is sinking. Giving back all of its 5.7% gain from last week, shares of USA Rare Earth (USAR -0.84%) have been in free fall this week. Several news events out of the rare-earth-mining industry have investors feeling less than bullish on the stock's prospects. According to data provided by S&P Global Market Intelligence, shares of the metals stock have plunged 18% from the end of last Friday's trading session through 12:25 p.m. ET on Thursday. The week began o ...