A polymorph of Al(OH)3 that occurs rarely in nature. The gibbsite Al(OH)3 octahedral layer is similar to the dioctahedral layer in bayerite, but the stacking of the layers differs. Small distortions in the bayerite octahedra produce an overall two-layer structure. A notable occurrence for bayerite is in sedimentary rocks from Hartrurim, Israel, where bayerite is in association with calcite, gypsum, portlandite, and ettringite.
Cf., gibbsite, nordstrandite