Between 1862 and 1866 pitch black heavy rains fell on Slains parish 7 times. Two showers were accompanied by large rafts of pumice stones on the sea (8-10in diam. and >1lb in weight). Attributed to Etna and Vesuvius eruptions, it fell nowhere else in Scotland*.
*Carluke, Lanark got one black rain at the same time (no pumice) but that’s some pinpoint accuracy for volcanic meteorological phenomena. The true cause was hotly debated in the papers but never settled Needless to say, parishioners in Slains lost their shit.