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

Narrower term/s

• pumice (volcanic rock)[+]
  • tezontle
• obsidian[+]
  • marekanite
• perlite
• tachylite
• pumice (pigment) [NP]

Anotations

Scope note:

A volcanic igneous rock of vitreous or glassy texture; it is a natural glass produced by the cooling of molten lava, or some liquid fraction of it, too quickly to allow crystallization.