Joan is a very generous fellow, because he parted with four little gems that he had picked up in the rubble of Pompeii.
Light and small pumice like the one above rained for 18 hours, and while the pumice rain was not a direct threat to human life, it accumulated to probably more than eight feet, causing roofs to collapse and buildings to fill with the equivalent of heavy Styrofoam pellets.
By the morning of August 25, the residents still in Pompeii realized that the city was uninhabitable. There was a mass exodus, but for those who had remained, it was already too late. The second, or Peléan phase of eruption started. (Peléan is a reference to the observations of the 1902 eruption of Martinique's Mount Pelé.)
In that phase the 18-hour column collapsed and a glowing cloud of high-temperature gas and dust raced down Vesuvius at approximately 60 mph (100 km), killing anyone who remained in its path.
I will be proud to permanently display these interesting and historic artifacts in the Pompeii Room when it is completed!
A 2018 Postscript: Archeologists have determined that the Vesuvius eruption that destroyed Pompeii actually occured in mid-to-late October of 79 A.D., not August.