The "peperino" rocks. Historical and volcanological overview

The name peperino derives from the Italian word pepe (from the Latin word piper, pepper) and has been used in the common language for lithified volcanic deposits characterized by light grey through dark grey tones and granular textures, resembling that of ground pepper. Among these, the best-known examples are represented by some phreatomagmatic deposits of the Colli Albani Volcanic District, near Rome (Italy), and ignimbrite deposits of the Cimini Mountains near Viterbo (Northern Latium, Italy), which have been widely employed in artefacts of historical and archaeological interest. In particular, these resistant volcanic rocks have been widely employed by the Etruscans and Romans since the seventh century BCE to produce sarcophagi and dimension stones, as well as architectural and ornamental elements. These rocks are still in use for building ornaments, street furniture and artworks in central Italy today. In this review, we provide an overview of the use of this term, and an exhaustive review of the different rocks of central Italy defined as peperino, describing their distinctive textural features, as well as their eruptive sources and outcrop areas. Indeed, despite the common macroscopic aspect, peperino rocks can be associated with several different eruptive styles and emplacement mechanisms. Our review is also addressed to archaeologists concerned with restoration initiatives and provenance studies, as well as to volcanologists studying the genetic processes of pyroclastic rocks and related naming conventions.