The glass (which is mostly SiO₂) in this decorative duck sculpture is amorphous. At the molecular level it is chaotic and disorganized. It lacks the long-range, repeating crystalline structure that is characteristic of a crystalline solid.

Quartz (SiO₂) is a crystalline material. It is not amorphous. Its crystalline structure can be seen on a macroscopic level as well as in the repeating network of regularly-spaced tetrahedral silicon atoms joined by divalent oxygen atoms through the sample. Shown here is a type of quartz called amethyst due to the purple coloration. The black material is hematite, an iron oxide. The specimen was mined in Mexico.