Silicified

Considerable changes in the chemical composition of rocks occur during the advanced argillic alteration. For example, Si02 content of highly silicified rocks of the Ugusu silica mine reaches 99% (Iwao, 1962). This silicification is caused by the considerable leaching of elements from the rocks by acid hydrothermal solution except Si and addition of Si from hydrothermal solution. 

The fluid inclusions can be divided into two types vapor- and liquid-rich fluid inclusions. The filling degree of fluid inclusions from some samples from the silicified and alunite zones is variable and homogenization temperatures vary widely. This indicates... 

Hydrothermal alteration in the Osorezan area is extensive. At the foot of the lava dome, highly silicified alteration occurs. From this zone towards marginal parts, kaolinite zone and montmorillonite zone exist. This type of alteration was caused by the acid hydrothermal solution. But at present such acid hot solutions are not present in the Osorezan area. The acid solution is considered to be of volcanic origin. It is therefore thought that the water chemistry evolved from extremely acid at the early stage to neutral pH at present (Aoki, 1992a). 

In contrast, such approaches have been much more developed with proteins, termed silicateins, that have been extracted from some silicified sponges [38]. The success of these approaches probably originates from the fact that the reactivity of these proteins towards silica precursors differs significantly from the processes occurring in diatoms. Whereas silaffins and poly-amines activate silica formation via electrostatic interactions due to the presence of positively-charged ammonium... 

Gawler Craton, located on the edge of the Great Victoria Desert (GVD). In this part of the GVD, regolith landforms are comprised of scarce hills of weathered bedrock outcrops surrounded by sand spreads, dunes and colluvial materials the hills act as windows to the otherwise covered weathered bedrock. The outcrops themselves have been silicified and, more recently, have been overprinted with calcrete. Calcrete sampling is relatively easy on the exposed outcrops and is preferentially sampled by mineral explorers due to its near-surface location (<10-20 cm depth). However, calcrete on the colluvial slopes and in the swales is not as easily located because of concealment by GVD sand and colluvium. 

Five E-W and N-S transects were selected for the GPR survey. These were located below the flanks of a low hill strewn with silcrete and silicified weathered bedrock cobbles and gravels. Previous limited drilling indicated that the thickness of exotic sandy cover was about 5 m and that calcareous materials may be patchily distributed. 

Sangster AG, Hodson MJ, Parry DW, Rees JA. A developmental study of silicifi-cation in the trichomes and associated epidermal structures of the grass Phalaris canariensis L. Ann Bot 1983 52 171-197. 

The Hackett River VMS deposits are hosted within the Ignerit Formation and are part Yellowknife Supergroup within the Slave Craton. The Ignerit Formation consists of highly silicified felsic volcanic rocks of calc-alkaline affinity that are intercalated with discontinuous lenses of calc-silicate that are interpreted to be tuffs... 

Most of the deposits are conformable with the Key Tuffite, a silicified tuff with a thickness ranging from 0.3 to 20 m, and traceable throughout the camp. 

Improved magnetotelluric methods have detected deep conductors and shallow alteration zones in the search for deep unconformity-related deposits (Farqu-harson Craven 2008). Clay-rich, quartz-corroded quartz-arenite has relatively low resistivity, whereas quartz-rich silicified zones are characterized by high resistivity. Although expensive, 3D seismic has been used to image details of basement topology and more favourable areas for drilling. 

Lignin-derived compounds have been observed in pyrolysis products of low rank coals and associate woody tissue FI- 61. Mycke and Michaelis [2] isolated lignin-derived methoxyphenols from a Miocene coal by catalytic hydrogenolysis. Sigleo [S] reported the presence of phenolic compounds derived from iteration of lignin in pyrolysis products of silicified woody tissue as old as Triassic age. However,... 

Guo M, Augsburger LL. Potential application of silicified microcrystalline cellulose in direct-fill formulations for automatic capsule-filling machines. Pharm Dev Technol 2003 8(l) 47-59. 

The essential difference between physical and chemical interactions is that in the former the interacting molecules are not chemically modified in any way. Hydrogen bonding may change, but there are no chemical changes that create a different molecule. However, this does not mean that the different components of the interaction can be easily separated the resultant mixture may be so intimate that separation is not possible. For example, silicified microcrystalline cellulose after processing cannot be separated entirely into its two separate components (fumed silica and microcrystalline cellulose). But on examination, using a number of vibrational spectroscopic methods, it was shown to be an intimate physical mixture and not a new chemical entity (8). 

Tobyn MJ, McCarthy GP, Staniforth JN, Edge S. Physicochemical comparison between microcrystalline cellulose and silicified microcrystalline cellulose. Int J Pharm 1998 169 183-194. 

Sherwood BE, Becker JW. A new class of high functionality excipients silicified microcrystalline cellulose. Pharm Tech 1998 22(10) 78—88. 

Steele DF, Edge S, Tobyn MJ, Moreton RC, Staniforth JN. Adsorption of an amine drug onto microcrystalline cellulose and silicified microcrystalline cellulose samples. Drug Dev Ind Pharm 2003 29(4) 475 487,... 

Moreton RC. Cellulose, silicified microcrystalline. In Kibbe AH ed. Handbook of Pharmaceutical Excipients. Washington, D.C. American Pharmaceutical Association and London Pharmaceutical Press, 2000 110-111. 

Substitution. This is a process whereby silica replaces wood liber to form silicified ipcirificdl wood, Quartz replacing ffnoriie is another example. In the latter instance, the original fluorine til the lluoriie is removed by silica-rich solutions lhal Itrsl remove the llunrinc and then substitute silica in its place. 

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