Actually you need to combine the smoothing and subdivision steps. (Subdivide, then smooth). And you shouldn't need such drastic subdivision as you describe.
Attached zip file contains Gold Brick.blend file that shows modeling and texturing for gold bar (Textures included) , plus OBJ model for basic ingot shape as rendered in Terragen and Gold_Brick.OBJ model of gold brick with subdivision, smoothing and texture applied and rendered in Terragen. See if it works for you on your system
P.S. You might also want to check to be sure that "soft shadows" is turned on and resolution is set to around four (or higher). If the soft shadowing is off and the render resolution is low then it's very possible that black patches will appear on the object.