Graphite mines in the United States largely closed down seven decades ago. Mining the ubiquitous mineral found in everything from nuclear reactors to pencils seemed to make little sense when it could be imported inexpensively from other nations, especially China.That view is changing now.Demand for graphite, a key material in the lithium-ion batteries that power everything from phones to electric cars, is surging as trade tensions with China persist. With federal officials concerned about the steady supply ...