Gold has a density (at room temperature) of approximately 19.30 grams per cubic centimeter; for tungsten, it's 19.25 grams per cubic centimeter. You'd have to have handled many 10 oz. gold bars to spot the difference, I'd think.
Not to mention that it would be pretty easy to size the tungsten to compensate and fool someone with a good scale. The size difference would be tiny. Or just plate it until you get the exact 10oz...