Global commodity markets are being rattled again by a familiar force: China’s army of cash-rich investors, The Wall Street Journal reports. A renewed rush into Chinese commodity futures is encouraging wild swings in prices for products including coal, iron ore and rubber, raising concerns about the return of a speculation frenzy. The price paid for physical iron ore has risen by about a quarter in the past week to its highest level in more than two years. Analysts and traders have linked the rally to renewed bets by Chinese speculators. On Monday, iron-ore futures on China’s Dalian Commodity Exchange rallied for an eighth consecutive session, rising 4.1% to 627 yuan ($91.62) a metric ton after briefly hitting the maximum-allowed gains for the day in overnight trading.