How to make fake gold bars

Now that the economy is collapsing, investors are becoming more interested in gold. Here's an item from PopSci that says it wouldn't be too difficult to make convincing fake gold bars out of gold-plated tungsten (which costs $30 a pound compared to $12,000 a pound for gold).
start with a tungsten slug about 1/8-inch smaller in each dimension than the gold bar you want, then cast a 1/16-inch layer of real pure gold all around it. This bar would feel right in the hand, it would have a dead ring when knocked as gold should, it would test right chemically, it would weigh *exactly* the right amount, and though I don't know this for sure, I think it would also pass an x-ray fluorescence scan, the 1/16" layer of pure gold being enough to stop the x-rays from reaching any tungsten. You'd pretty much have to drill it to find out it's fake.
Link (Via Museum of Hoaxes)