The substance may come as anhydrous or hydrated salt with varying properties.

The anhydrous salt has good solubilty in water (~10% or more at 25°C) and contains 16.2% elemental magnesium by weight.

[1] This form doesn't have any noticeable taste.

Commercially available are the anhydrous salt, as well as nonahydrate (with 9 molecules of water attached) and 14-hydrate.

[2] The nonahydrate form contains 12% elemental magnesium by weight.