By The Associated PressPLATINUM RISING: Platinum and palladium surged Tuesday on renewed concerns that supplies of the platinum group metals will shrink. Both metals climbed more than 1 percent. ZIMBABWE FACTOR: Zimbabwe's government reportedly gave platinum producers two years to begin refining the metals in Zimbabwe. That spurred speculation on Tuesday that production of platinum will drop, because the companies will likely have to build the refineries. CROP DROP: Grain prices edged lower. Corn fell 6 cents to $6.9625 a bushel while wheat dropped 9.5 cents to $7.32 a bushel. Soybeans fell 10.7 cents to $14.2075 per bushel.