Hierarchy classification:

1. top of the aat hierarchies
2. Materials Facet
3. Materials (hierarchy name)
4. materials (substances)
5. [materials by form]
6. [materials by chemical form]

Anotations

Scope note:

Structurally distinct forms in which a chemical element may occur. Some chemical elements may exist in two or more different forms, in the same physical state. Allotropes are different structural modifications of an element; the atoms of the element are bonded together in a different manner.