The U. S. is taking a minority stake in an Oklahoma rare earth miner, the latest government investment in the sector as it seeks to minimize its reliance on imports of a material used prevalently in smartphones, robotics, electric vehicles and many other high tech products. China processes more than 90% of the world’s critical minerals and has used its dominance in the market to gain leverage in the trade war with Washington. USA Rare Earth said Monday that the U. S. Commerce Department is 6...