A former undergraduate student gave me this in the 1990s sometime. I’m 'blanking' on who gave it to me. She found it in the Rillilto River in Tucson while hiking. I like the range of history that is bound up in this rock: so many different chapters are preserved.
Age & Formation
The granule conglomerate probably came from Miocene fanglomerate, ~25- 20 Ma. Faulting and vein-filling is probably no older than ~18 Ma.