Mount Vesuvius, Naples, Italy is the type locality of euchlorine. It occurred as a sublimate in fumaroles (hot vents of steam and other volcanic gases) that formed during the 1868 volcanic eruption, it has also been found in fumaroles during eruptions at the same location in 1892 and 1893. Mineral associations at this site include dolerophanite, eriochalcite, chalcocyanite, melanothallite, anglesite, atacamite, cryptochalcite, palmierite, barite, and natrochalcite.