This mining company is up over 400% year over year -- should you buy now?Shares of The Metals Company (TMC 1.62%) have whipsawed this summer.First came a surge after Korea Zinc, a non-ferrous metal smelter based in South Korea, announced an $85.2 million investment in TMC -- the company's first major endorsement from an industry partner. Then came another pop after the National Oceanic and Atmospheric Administration (NOAA) reconfirmed that TMC's exploration applications are in compliance under U.S. law.Then ...