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. metamorphic rock
9. serpentinite

Anotations

Scope note:

An extremely heavy sepentinite having the form of a flattened sphere, its name deriving from the Greek word for kidney. The rocks were used by the ancient Romans as standard weights and were also supposedly tied around the necks of condemned Christians before they were drowned, explaining why it is sometimes referred to as martyr's stone. It is most commonly jet black with small specks of gray and a metallic texture.