tuff - rhyolitic tuff with pumice clasts - a classic ignimbrite or pumice-dominated pyroclastic deposit - teaching hand/display specimen

This particular volcanic igneous rock, the Bishop Tuff, is composed of volcanic ash and fragments of pumice that were ejected as a pyroclastic flow from vents near Mammoth, California 700,000 years ago. It is a classic example of an ignimbrite, where the ash was ~600˚C , causing the ash and pumice fragments to weld together. The Bishop tuff is variable. These specimens were collected in one area where it contains considerable numbers of darker pumice clasts (from klastos, Greek = broken in pieces). In other areas, the clasts are angular fragments of various igneous rocks ripped violently from the walls of the vent. The term “ignimbrite” was coined by the New Zealand geologist Peter Marshall in 1935. This term was originally used only to refer to welded tuffs. These are pyroclastic rocks that were so hot right after the deposition from the pyroclastic cloud that individual clasts adhered to each other. However, this restriction no longer applies. This is a self-teaching tuff. It looks a