Although wadsleyite does not contain H in its chemical formula, it may contain more than 3 percent by weight H2O, and may coexist with a hydrous melt at transition zone pressure-temperature conditions.

Furthermore, the transformation resulting in wadsleyite is thought to occur also in the shock event when a meteorite impacts the Earth or another planet at very high velocity.

Wadsleyite was first identified by Ringwood and Major in 1966 and was confirmed to be a stable phase by Akimoto and Sato in 1968.

In values of weight percent oxide, the pure magnesian variety of wadsleyite would be 42.7% SiO2 and 57.3% MgO by mass.

An analysis of trace elements within wadsleyite shows a large number of elements: rubidium (Rb), strontium (Sr), barium (Ba), titanium (Ti), zirconium (Zr), niobium (Nb), hafnium (Hf), tantalum (Ta), thorium (Th), and uranium (U).

If water incorporation exceeds about 1.5% the M3 vacancies can be ordered in violation of space group Imma, reducing the symmetry to monoclinic I2/m with beta angle up to 90.4º.

[citation needed] Wadsleyite II is a separate spinelloid phase with both a single (SiO4) and double (Si2O7) tetrahedral units.

It is a magnesium-iron silicate with variable composition that might occur between the stability regions of wadsleyite and ringwoodite γ-Mg2SiO4,[14] but computational models suggest that at least the pure magnesian form is not stable.

Because of small crystal size, detailed optical data could not be obtained; however, wadsleyite is anisotropic with low first-order birefringence colors.