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. igneous rock
9. [igneous rock by origin]
10. extrusive rock
11. pyroclastic rock
12. tuff

Narrower term/s

• sperone

Anotations

Scope note:

Ash, gravel, and volcanic material that have been closely welded together to form a rock that is characteristically dark greenish gray and studded with black fragments that resemble peppercorns, hence its name. It is used for stairs and fountain bases because it becomes more consistent when wet. Susceptible to heat and frost, it is only found in great condition underground. Quarries for this rock are found near Albano and the Castle of Marino in Italy.