peperine

from The Century Dictionary.

• noun A volcanic tufa composed of well-developed crystals or crystal fragments cemented together. The name was first given to the tufas of the Alban Mount, near Rome.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Geol.) A volcanic rock, formed by the cementing together of sand, scoria, cinders, etc.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Alternative form of peperino.