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The polymorphs differ in terms of the stacking of the layers. All forms of Al(OH) 3 crystals are hexagonal [disputed – discuss]: gibbsite is also known as γ-Al(OH) 3 [8] or α-Al(OH) 3 [citation needed] bayerite is also known as α-Al(OH) 3 [8] or β-alumina trihydrate [citation needed] nordstrandite is also known as Al(OH) 3 [8] doyleite
corundum (Al 2 O 3) aluminium oxide hydroxides diaspore (α-AlO(OH)) boehmite or böhmite (γ-AlO(OH)) akdalaite (5Al 2 O 3 ·H 2 O) (once believed to be 4Al 2 O 3 ·H 2 O), also called tohdite; aluminium hydroxides. gibbsite (often designated as γ-Al(OH) 3, but sometimes as α-Al(OH) 3, [4] sometimes called hydrargillite or hydrargyllite)
Gibbsite has three named structural polymorphs or polytypes: bayerite (designated often as α-Al(OH) 3, [2]: 2 but sometimes as β-Al(OH) 3) [citation needed], doyleite, and nordstrandite. Gibbsite can be monoclinic or triclinic, while bayerite is monoclinic. [2]: 13 Doyleite and nordstrandite are triclinic forms. [2]: 13
When the Bayer liquor is cooled, Al(OH) 3 precipitates, leaving the silicates in solution. NaAl(OH) 4 → NaOH + Al(OH) 3. The solid Al(OH) 3 Gibbsite is then calcined (heated to over 1100 °C) to give aluminium oxide: [7] 2 Al(OH) 3 → Al 2 O 3 + 3 H 2 O. The product aluminium oxide tends to be multi-phase, i.e., consisting of several phases ...
Boehmite or böhmite is an aluminium oxide hydroxide (γ-AlO(OH)) mineral, a component of the aluminium ore bauxite.It is dimorphous with diaspore.It crystallizes in the orthorhombic dipyramidal system and is typically massive in habit.
The formula, Cu 2 CO 3 (OH) 2 shows that it is halfway between copper carbonate and copper hydroxide. Indeed, in the past the formula was written as CuCO 3 ·Cu(OH) 2. The crystal structure is made up of copper, carbonate and hydroxide ions. [37] The mineral atacamite is an example of a basic chloride. It has the formula, Cu 2 Cl(OH) 3.
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Doyleite grows in small square tabular crystals, which form rosettes. Individual crystals can grow up to 8 mm. The mineral has a layered micaceous structure. [4] This pinacoidal mineral mostly consists of oxygen (61.53%) and aluminum (34.59%), but also contains hydrogen (3.88%).