Gibbsite


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Related to Gibbsite: goethite, diaspore, boehmite, Brucite

gibbsite

[′gib‚zit]
(mineralogy)
Al(OH)3 A white or tinted mineral, crystallizing in the monoclinic system; a principal constituent of bauxite. Also known as hydrargillite.

Gibbsite

 

(also hydrargillite), a mineral with the chemical composition Al[OH]3. It contains 65.4 percent alumina (A1203); admixtures of Fe3+ and Ga3+ that replace Al3+ in the structure are known. Gibbsite crystallizes in a monoclinic system. Its crystalline structure is of the layer type and consists of bifoliate (OH) packets, in the midst of which Al3+ ions are distributed. Good cleavage occurs along weak interpacket bonds. Gibbsite forms small laminar crystalline particles, usually colorless with a pearly luster, as well as powdery aggregates and incrustations with a radiated or imbricate microstructure. Its hardness on the mineralogical scale is 2.5-3.5; its density is 2,300-2,400 kg/m3. It usually forms upon weathering of alumina-rich rocks. Together with the other hydroxides of aluminum (diaspore and boehmite) and iron, gibbsite is found in bauxite ores. Gibbsite bauxites are among the best aluminum ores.

References in periodicals archive ?
The observed lower capacity of kaolinite to adsorb P compared with that of gibbsite (BARBIERI et al., 2009; BROGGI et al., 2010; CESSA et al., 2009; FONTES; WEED, 1996) has been related to the lower concentrations of OH sites on its surface (CELI et al., 2003).
A great deal of effort has been expended in intensifying gibbsite precipitation from sodium aluminate liquor and progress has been achieved.
The considerable sensitivity of this method is evident from different chemical shifts of three Al minerals (Table 2, corundum, gibbsite and kaolinite, see below).
As stated above, the mineral composition of residue sand is dominated by quartz, with lesser amounts of hematite, gibbsite, goethite, and amorphous Fe and A1 oxides, and these materials exhibit a PZNC of ~3, 8.5, 9.8, 8.8, 8.0, and 9.3, respectively (Theng 1980; Goldberg et al.
For CAC, the solubility products for the hydrates Katoite and Gibbsite are low.
At variance with these results, a previous [sup.31]P magic angle spinning NMR and surface complexation modelling study suggested that two outer-sphere ternary complexes can be formed on gibbsite in the presence of both IHP and Cd(II), and the predominant one is dependent on the adsorbate concentration (Ruyter-Hooley et al.
The first weight loss of 12.51% from 25 to 139[degrees]C was ascribed to the physically adsorbed water; the second weight loss of 8.02% from 139 to 294[degrees]C may be due to gibbsite and Fe hydroxide (formed in the homogeneous precipitation process during catalyst preparation) decomposing into [gamma]-[Al.sub.2][O.sub.3] [46] and hematite, respectively; the third weight loss of 6.36% in the temperature range from 294 to 800[degrees]C was attributed to decomposition of the remaining hydroxides.
Equatorial and tropical weathering of recent basalts from Camerroon: allophanes, halloysite, metahalloysite, kaolinite and gibbsite, pp.
At pH >5.6, naturally occurring aluminium compounds exist predominantly in an undissolved hydroxide form such as gibbsite [Al[(OH).sub.3]] or as aluminosilicates.
This has resulted in the separation of the gibbsite octahedral and silicon tetrahedral layers.
At the interface the minerals Apatite, Calcite and Gibbsite were found, whereas in the bulk Gibbsite and Katoite were present.
In some samples aluminium hydroxide (gibbsite) was added to the initial ash.