Huemulite
Huemulite is a mineral with formula Na4Mg(V10O28)·24H2O that is yellow to orange in color. It was first discovered in Argentina in 1959 and described in 1966. The mineral is named for the Huemul mine in which it was discovered. Occurrence and properties Huemulite is yellowish orange to orange and bright in color. The mineral occurs as thin films, aggregates of fine fibers, botryoidal masses, and interstitial filling in host sandstone. Huemulite has been found in Argentina, the Czech Republic, the United Kingdom, and the United States. It occurs in association with epsomite, gypsum, hummerite, rossite, and thenardite. Huemulite is a member of the pascoite group. It melts at to become a red liquid. Huemulite dissolves readily in cold water to produce an orange-yellow solution with a pH of 5.5 to 6.5. Formation and synthesis In Argentina, the mineral formed after mine tunnels were cut through Cu-U deposits in sandstone and conglomerate. The vanadium in huemulite is thought to originate from asphaltic material that occurs in association with the sandstone. Huemulite can be synthesized by mixing stoichiometric proportions of vanadium pentoxide, magnesium carbonate, and sodium carbonate in cold water in a humid environment. The mixture is heated to dissolve the compounds