Diaspore clay

High Alumina. The naturally occurring raw materials are bauxites, sillimanite [12141 5-6] group minerals, and diaspore clays (see Aluminum compounds). Other high alumina raw materials are made by beneficiation, blending, and other processing techniques. 

High Alumina Clay Minerals. Several hydrated alumina minerals should be grouped with the clay minerals because the two types may occur so intimately associated as to be almost inseparable. Diaspore (a-AIO(OH)) and bochmitc (y-AIO(OH)). both AFOj H 0(AI Oi. 85% H 0. 15%) are Ihe chief constituents of diaspore clay, which may contain over 75% AhOj on the raw basis. Gibbsite, AliOj 3 HyO (AljOi. 65.4% HjO. 34.6%). and cliachite. the so-called amorphous alumina hydrate (much cliachite is probably cryptocryslalline), as well as Ihe monohydrates, occur in hauxile, bauxitic kaolin, and bauxitic clays. 

Alumina. The naturally occurring raw materials are bauxites, sillimanite group minerals, and diaspore clays (see Aluminum). 

Burley Clay. A refractory clay, intermediate in alumina content between a flint clay and a diaspore clay, that occurs in Missouri, USA elsewhere it is known as Nodular Fireclay. The name derives from the diaspore oolites, known... 

The possible content of hydrated alumina and iron. Hydrated alumina minerals like gibbsite [14762-49-3] Al(OH)2, boehmite [1318-23-6] AlOOH, and diaspore [14457-84-2] AlOOH, occur ia bauxitic clays. Bauxites grade chemically iato hydrated fermgiaous and manganiferous laterites. Hence, finely divided M2O2, usually hydrated, may be a significant constituent of a clay where M may be A1 or Fe. Hydrated colloidal s ica may play a role ia the sHppery and sticky properties of certain clays. 

High alumina clays refer ia the ceramic iadustries to nodular clays, budey-flint clay, budey and diaspore, gibbsitic or bauxitic kaolins (clays), abrasive clays, and others. Siace the depletion of diaspore varieties ia Missouri and Pennsylvania, most bauxitic kaolin and clay is produced ia Alabama and Arkansas. 

Francombe, M.H. Rooksby, H.P. (1959) Structure transformation effected by the dehydration of diaspore, goethite and -ferric oxide. Clay Min. Bull. 4 1-14... 

Practically all world production of newly smelted aluminum was made from bauxite. The term bauxite is used for naturally occurring mixtures of aluminum monohydrate (boehmite or diaspore) and trihydrate gibbsite Al(OH)3, including impurities which are typically clay minerals, free silica, iron hydroxides and titania. The luminescence ofboehmite and diaspore and LIBS (Fig. 8.10) maybe used for the detection, sorting and commercial value evaluation of A1 minerals. 

Alkali leach methods axe exemplified by the Bayer process for the preparation of pure a-A C for electrolysis (Section 17.5) from the mineral bauxite. Bauxite consists mainly of a-AlO(OH) (diaspore) and/or 7-A10(0H) (boehmite), the difference between these being essentially that the oxygen atoms form hep and ccp arrays, respectively. The chief contaminants are silica, some clay minerals, and iron(III) oxides/hydroxides, which impart a red-brown color to the mineral. Aluminum (III) is much more soluble than iron(III) or aluminosilicates in alkali, so that it can be leached out with aqueous NaOH (initially 10-15 mol L 1) at 165 °C under approximately 0.6 MPa pressure, leaving a red mud of iron (and other transition metal) oxides/hydroxides and aluminosilicates ... 

Bauxite is a mixture of minerals and contains e.g. diaspore [a-AlOOH], gibbsite [y-Al(OH)3], iron hydroxides, clay minerals and quartz. 

Aluminium oxide is the oldest ceramic material used in medicine. Bauxite and corundum are the main natural sources of aluminium oxide. Bauxite is a mixture of diaspore, gibbsite, iron hydroxides, clay minerals and quartz. It is formed by the tropical weathering of silicate rocks during which quartz and the elements sodium, calcium, magnesium and potassium are largely washed away. This is the reason why the remaining material becomes richer in the resistant elements titanium, iron and aluminium. The latter is extracted from this mixture in the form of aluminium hydroxide. In its turn this compound is converted into aluminium oxide by heating the mixture to 1200-1300 °C, this is called calcination. The hydroxide is thus made anhydrous. 

Fire clays, ball clays, flint clays are kaolinite-rich clays, usually of the 6-axis disordered variety, which contain a relatively high impurity content. Illite, montmoril-lonite, diaspore, boehmite, quartz, and organic material are the minerals usually associated with these deposits. Few, if any, of the kaolinite minerals in these clays have been concentrated enough to afford meaningful chemical data. 

There are two well-known oxide-hydroxides (AlOOH) with closely related structures diaspore and boehmite. Diaspore occurs in some types of clay and bauxite. It has been produced by the hydrothermal treatment of corundum, a-Al203. Whereas boehmite is characterized by cubic close-packing of the anions, diaspore has a hexagonal close-packed structure. This difference probably accounts for the direct thermal transformation of diaspore to corundum at relatively low temperatures (450-600°C). 

Diaspore, o -AlO(OH), occurs in some types of clay and bauxite and can be synthesized by hydrothermal treatment of boehmite, y-AlO(OH), in 0.4% aqueous NaOH at 380 °C and 500 atm. Crystalline boehmite is easily obtained upon warming the amorphous, gelatinous precipitate that forms when cold solutions of aluminum salts are treated with ammonia. 

The most widespread fill material is reddish brown (2.5 YR 4/4, 5 YR 4/4) loam with a minor admixture of relatively large oolitic bauxite pebbles (derived from the Late Triassic - Camian - beds) and coarse clasts of black chert. Pilot X-ray diffraction analysis revealed mostly muscovite/illite, plus mixed-layer clay minerals of illite/montmorillonite type, chlorite plus mixed-layer clay minerals of chlorite/montmorillonite type, calcium montmorillonite, and diaspore plus gibbsite, or just traces of bauxite minerals (Misic, 2000). The mineral composition is not as uniform as might be expected, and further research, intended for application of factorial analysis, is in progress. A potential sediment source area in the present Cerkniscica River basin (Fig. 1) appears obvious at first glance, but similar outcrops of bauxite and chert do also appear at other sites that are not much more remote. 

Natural kaolin is treated by washing, in order to remove the coarser particles and impurities such as quartz, feldspars, etc. For some purposes, use is also made of crude kaolin (e.g. in fireclay manufacture). Clays are more widespread in nature they are usually contaminated with larger amounts of quartz, feldspar, mica, etc. Clays containing larger or smaller amounts of aluminium hydroxides (diaspore or gibbsite) occur and are used as ceramic raw materials in some countries. 

Oliver PM, Watson GW, Kelsey ET, Parker SC (1997) Atomistic simulation of the surface structure of the Ti02 polymorphs ratile and anatase. J Mater Chem 7 563-568 Penn RL, Banfield JF, Kerrick DM (1999) TEM investigation of Lewiston, Idaho, fibrolite microstructure and grain boundary energetics. Am Mineral 84 152-159 Peiyea EJ, Kittrick JA (1988) Relative solubility of corandum, gibbsite, boehmite, and diaspore at standard state conditions. Clays Clay Minerals 36 391-396... 

Aluminium hydroxyoxides. These include gibbsite (Al(OH)3), boehmite and diaspore (AlOOH), and allophane. The loss of silicon from soils leaves an Aland Fe-rich residue in soil clays. 

Associated minerals These mineral constituents do not impart plasticity to clay. Examples include silicate minerals like micas, quartz, feldspars etc. iron oxides and hydroxides like magnetite, hematite, maghemite, goethite, lepidoerocite etc. and aluminium oxides and hydroxides like corundum, gibbside, boehmite, diaspore etc. 

Do not impart plasticity to clay, do not harden upon dryingAiring. M neote. hematite, goethite, gibbside, boehmite, diaspore etc. 

Clay minerals Associated minerals Import plasticity Do not import plasticity Hardens on drying/firing Kaolinite, montmorillonite, illite, vermiculite, palygorskite etc. Magnetite, hematite, maghemite, goethite, lepidocrocite gibbside, boehmite, diaspore. 

Laterites, the source of Al-ore exists laigly in clay minerals. Gibbsite, bohemite, and diaspore are the Al-hydroxides which provide a major source of A1 and Fe ores. 

Diaspora clay. This is a high-alumina material containing 70 to 80 wt.% Al Oj after firing of a mixture of diasporic bauxite and clay. 

Flint Clay. A non-plastic refractory clay of a type found in Missouri (USA), Southern France, and a few other localities. Flint clays are kaolinitic, but laterization (See laterite) has occurred so that the Missouri deposit, for example, may also contain diaspore whereas the French may contain boehmite. Flint clays contain (fired) 40-45% AI2O3 P.C.E. 34-35. 

The aluminum hydroxide (gibbsite, y-Al(OH)3) and oxyhydroxide (boehmite, y-AlOOH diaspore a-AlOOH) minerals in bauxite ore are selectively extracted from the insoluble components (mostly quartz, clay minerals, and iron and tita-... 

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