Illustrated Glossary of Organic Chemistry

Amorphous: A substance that lacks long range (throughout the entire sample) crystalline structure.

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.