Tungsten pentoxide was reported in early literature but proved to have the stoichiometry W₁₈O₄₉. Sometimes called mineral blue it is a blue solid formed by the reaction of tungsten trioxide, W₂O₃, and tungsten metal at 700 °C. There are a number of these unusual intermediate oxides formed from reacting metal and trioxide namely, W₂₀O₅₈,W₂₄O₇₀. W₁₈O₄₉ contains both octahedral and pentagonal bipyramidal coordination of the metal atoms by oxygen.