Gold prices plunged in New York Thursday as cash and government bonds proved the only attractive investment for the day. The Dow Jones industrial average dropped 391 points or 3.51 percent in a global sell-off that saw markets tumble in Asia and Europe. The dollar index gained 0.91 percent to 78.39. The benchmark 10-year treasury note rose 1/1132 to yield 1.723 percent. On the Comex division of the New York Mercantile Exchange, gold gave up $66.90 to reach $1,741.20 per troy ounce. September delivery silver lost $3.88 to $36.54 per troy ounce The euro fell to $1.3466 from Wednesday\'s $1.3572. Against the yen, the dollar fell to 76.21 yen from 76.44 yen. The British pound fell to $1.5343 from $1.5499. The U.S. standard was 7.8017 Hong Kong dollars from Wednesday\'s 7.7939 Hong Kong dollars. The U.S. dollar rose to 1.0285 Canadian dollars from 1.0083 Canadian. The Australian dollar fell to $0.9741 from $1.0043.