Crystal structure of the element Bismuth. This is how the metal forms in Nature. When Bismuth is heated to its melting point in a fire-proof bowl, as it begins to harden under the surface, the metal will take on this same form. Almost as if you are looking straight up through the bottom of a pyramid. The interior walls are off set, just as a pyramid is. The beautiful colors which are reflected back at the observer are stunning. Deep iridescent blues, greens and purples. Amazing natural sculpture