touchstone

  1. Home
  2. top of the aat hierarchies
  3. Materials Facet
  4. Materials (hierarchy name)
  5. materials (substances)
  6. [materials by composition]
  7. inorganic material
  8. rock (inorganic material)
  9. sedimentary rock
  10. [sedimentary rock by composition]
  11. chert
  12. flint (rock)
  13. touchstone
Scope note
A velvety-black variety of cryptocrystalline quartz, siliceous shale, or similar substance used by jewelers for testing the purity of precious metal, especially gold, by the streak left on the stone when rubbed with the metal.
touchstone
Accepted term: 18-Nov-2024