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]
7. elements (chemical substances)

Anotations

Scope note:

Elements found in minute quantities in minerals, not essential to their composition but found in their structure or adsorbed on their surface, conventionally held to constitute significantly less than 1.0% of the mineral. Use also for elements found in plant and animal tissue in concentrations of 1.0% or less, which are physiologically essential to the organism.