Shcherbinaite, naturally occurring V 2 O 5 , has been discovered in the high-temperature fumaroles of Izalco Volcano. El Salvador, and Bezymyanny Volcano, Kamchatka, U.S.S.R. The Izalco mineral occurs as euhedral golden-yellow needles and laths up to 1 cm in length. The crystals, which formed as sublimates from volcanic gases, are found coating basaltic breccia fragments in the summit crater fumaroles. The mineral is associated with bannermanite. An electron microprobe study of shcherbinaite demonstrates that the mineral is pure V 2 O 5 and contains no detectable impurities or alkali metals such as occur in solid solution in oxide bronze compounds. A comparison of the lattice parameters and crystal structures of shcherbinaite and synthetic V 2 O 5 shows that the compounds are essentially identical. All lattice parameters are within 1 standard deviation and all atomic positional and thermal parameters are within 2.3 standard deviations of those found in the synthetic compound.--Modified journal abstract.