Hierarchy classification:

1. top of the aat hierarchies
2. Materials Facet
3. Materials (hierarchy name)
4. materials (substances)
5. [materials by composition]
6. inorganic material
7. salt (inorganic material)

Anotations

Scope note:

Any of the salts of magnesium and phosphate, which may appear in monobasic, dibasic, or tribasic form. Deposits of magnesium phosphates bobierrite, newberyte and struvite are found in ivory artifacts and excavated mammoth and elephant tusks.