China, the leading producer of rare minerals, has made it harder in recent weeks for foreign companies, particularly chip makers, to buy such materials in China (Keith Bradsher/New York Times)

Keith Bradsher / New York Times: China, the leading producer of rare minerals, has made it harder in recent weeks for foreign companies, particularly chip makers, to buy such materials in China  —  Already the dominant producer of rare minerals, Beijing is using export restrictions and its power over state-owned […]