Diaspores

pseudocyphellae of Pseudocyphellaria Figs. 90-91, young and old cyphellae of Sticta sylvatica. (Figs. 89-91 from Henssen and Jahns, 1973.) 

soralium of Lobarta pulmonaria Fig. 93, respiration pore of Nephroma resupinatum Fig. 94, pseudocyphellae of Cornicularia divergens Fig. 95, pseudo-cyphellae of Cetrelia cetrarioides (Figs. 92-94 from Henssen and Jahns, 1973.) 

Development of Isidia. It is still unknown what factors cause the formation of isidia. In Peltigera praetextata it has been shown experimentally that the development of isidia or lobules is stimulated by the tearing or wounding of the thallus (Fig. 97). The development of isidia seems to be genetically determined. Their presence and shape is an important taxonomic characteristic. 

In Umbilicaria pustulata the cortex of the isidia (Fig. 96) is not formed secondarily but the cortex of the thallus grows upwards and surrounds the medullary tissue from their initiation. 

Soredia need not be confined to delimited soralia but can originate over the whole surface of a lichen, which assumes a powdery appearance (Fig. 36). True delimited soralia may be divided into several types on the basis of their shape (Bitter, 1901 Du Rietz, 1924 Frey, 1963)  

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Basic refractory materials include lime, magnesia, various materials composed chiefly of alumina (bauxite, diaspore, laterite, gibb-site, etc.), dolomite and most of the rarer refractory oxides, particularly zirconia. 

Gallium is often found as a trace element in diaspore, sphalerite, germanite, bauxite, and coal. Some flue dusts from burning coal have been shown to contain as much 1.5 percent gallium. 

GaOOH oxidation of Ga with H2O at ca 200°C, under pressure orthorhombic Pbnm (diaspore)... 

The CAS registry Hsts 5,037 aluminum-containing compounds exclusive of alloys and intermetaUics. Some of these are Hsted in Table 1. Except for nepheline and alunite in the USSR and Poland, bauxite is the raw material for all manufactured aluminum compounds. The term bauxite is used for ores that contain economically recoverable quantities of the aluminum hydroxide mineral gibbsite or the oxide—hydroxide forms boehmite and diaspore. 

Diaspore (P-Aluminum Oxide Hydroxide). Diaspore, found in bauxites of Greece, Cliina, and the USSR, can also be obtained by hydrothemial transfomiation of gibbsite and boehmite. Higher (>200°) temperatures and pressure (>15 AlPa-150bar) are needed for synthesis and the presence of diaspore seed cry stals helps to avoid boehmite fomiation. 

Under equiUbrium vapor pressure of water, the crystalline tfihydroxides, Al(OH)2 convert to oxide—hydroxides at above 100°C (9,10). Below 280°—300°C, boehmite is the prevailing phase, unless diaspore seed is present. Although spontaneous nucleation of diaspore requires temperatures in excess of 300 °C and 20 MPa (200 bar) pressure, growth on seed crystals occurs at temperatures as low as 180 °C. For this reason it has been suggested that boehmite is the metastable phase although its formation is kinetically favored at lower temperatures and pressures. The ultimate conversion of the hydroxides to comndum [1302-74-5] AI2O2, the final oxide form, occurs above 360°C and 20 MPa. 

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. 

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. 

In general the A—H B hydrogen bond can be taken to be approximately linear for example, in diaspore the angle between the inter-... 

The Y, C and B sub-types roughly correspond to types 1, 2 and 3 as defined by Urabe (1974a), who classified Kuroko deposits based on hydrothermal alteration and ore mineral assemblages type 1, kaolinite-pyrophyllite-diaspore-type type 2, sericite-chlorite-type type 3, sericite—chlorite-carbonate-type. Hydrothermal alterations in the Kuroko mine area are described in section 1.3.2. 

Pyrophyllite and diaspore alterations were reported from several Kuroko deposits, although they are not common (Urabe, 1974a). This type of hydrothermal alteration is thought to have occurred at a later stage than the hydrothermal alterations associated with Kuroko mineralization (sericite, chlorite, and zeolites) (Utada, personal communication, 1995). 

Oxides and hydroxides Cuprite, uraninite, baddeleyite, corundum, haematite, rutile, cassiterite, brucite, diaspore, goethite, limonite... 

The major raw materials used at present for the production of alumina are bauxites, which are found in the following mineral forms gibbsite (Al(OH)3), boehmite (AlO OH), and diaspore (AlO OH). The major impurities are the oxides of iron, silicon, and titanium, and organic compounds, all of which must be removed before alumina is suitable for aluminum production. The process objectives are, therefore, separation of impurities and compound production in the present case. Bauxite is first dried to facilitate grinding, destroy organic matter, and oxidize the associated ferrous minerals to the ferric state. The temperature of drying is not allowed to exceed 150 °C, because at higher temperature a part of the combined water is expelled and the solubility is affected adversely. 

Double strands of edge-sharing octahedra in diaspore, a-AlO(OH)... 

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