Tungsten pentoxide (W₂O₅) was reported in early literature but proved to have the stoichiometry W₁₈O₄₉.^[1] Sometimes called mineral blue, it is a blue solid formed by the reaction of tungsten trioxide, WO₃, and tungsten metal at 700 °C.^[1]

This article's factual accuracy is disputed. (February 2012)

There are a number of these unusual intermediate oxides formed from reacting metal and trioxide namely, W₂₀O₅₈, W₂₄O₇₀.^[1] W₁₈O₄₉ contains both octahedral and pentagonal bipyramidal co-ordination of the metal atoms by oxygen.^[1]

• Tungsten(III) oxide
• Tungsten(IV) oxide
• Tungsten(VI) oxide