http://www.nytimes.com/2008/01/31/science/31metal.html?_r=3&oref=slogin&oref=slogin

In a feat of optical alchemy, Dr. Guo, a professor of optics at the University of Rochester, and Anatoliy Y. Vorobyev, a postdoctoral researcher, use ultrashort laser bursts to pockmark the surface of a metal in a way that is not perceptible to the touch — it still feels smooth to the finger — but that alters how the metal absorbs and reflects light.

The result is that pure aluminum looks like gold, and the appearance is literally skin deep.