Why MP Materials Stock Crashed on Monday

President Trump's tariffs policy just tanked MP's stock.Reversing course after a terrific week preholiday, shares of rare-earth minerals miner MP Materials (MP -14.57%) gave back most of last week's gains on Monday, sinking 12.2% through 11:40 a.m. ET and returning its share price to where it sat roughly 10 days ago.The reason probably has a lot to do with President Donald Trump's tariff battle with China.MP Materials and the tariffsPresident Trump has raised tariffs on Chinese imports to about 145% over th ...