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. rock (inorganic material)
8. [rock by form]
9. stone (worked rock)
10. [stone by quality]
11. gemstone
12. [gemstones by specific type]

Anotations

Scope note:

Gemstone, comprising the skeletons of corals, typically those having red color and found in the Red Sea and Mediterranean, such as Corallium rubrum; prized from times of antiquity for ornamental purposes, and often classed among precious stones.