Real Materials

· The photograph shows the grains in the polycrystalline ceramic uranium carbide. The colors result from the etching process used to reveal the crystallites. The magnification is 300 times.
· Each crystallite has nominally the same composition. The different crystal faces have different etch rates, and the etching process reveals those surfaces that are most stable to the etchant.

From: Gilman, "The Nature of Ceramics," Scientific American, September (1967)