Whewellite

Kohlen-schwarz, n. carbon black charcoal black, -schwefelwasserstoffsaure, /, (tri)-thiocarbonic acid (H2CS1). -spat, m. anthraconite whewellite, -spitze,/. carbon point, -staub, m. coal dust charcoal dust, -stick-stoff, m. cyanogen, -stickstoffsaure, /, car-bazotic acid (picric acid), -stoff, m. carbon,... 

Werner s coordination theory, 1, 6 Whewellite structure, 6, 849 Wickmanite structure, 6, 849 Wilkinson s catalyst, 6, 239 Wilson s disease, 5, 721 copper, 6,648 removal, 6,769 copper complexes, 2,959 copper metabolism, 6,766 radiopharmaceutical agents, 6,968 Wolfram s red salt, 5,427 Wurzite... 

Oxalate Ca(C00)2H20 Ca(C00)2-2H20 Whewellite 1 Weddellite I " Insect eggs Vertebrate stones. .Abundant in plants Deterrent Cytoskeleton Ca store... 

Calcium oxalate (whewellite, weddelite) Gallstones plant defenses... 

Both calcium oxalate monohydrate and dihydrate - whewellite and weddelite - contain eight-coordinated Ca2+ in distorted square-antiprismatic geometry, but there is one coordinated water in the former, two in the latter. Whewellite has a layer structure through the sharing of three edges of each coordination square-antiprism with three adjacent polyhedra weddelite has a chain structure (128). The trihydrate also contains eight-coordinated Ca2+ (129). 

Calcium oxalate (723) occurs as the monohydrate (whewellite, the thermodynamically stable form under ambient conditions (724)), the dihydrate (weddellite) in plant calcium stores and in sap, or the trihydrate (725). Calcium oxalate also plays a structural role in plants. Oxalate, for example from excessive amounts of rhubarb or spinach, inhibits absorption of Ca2+ from the GIT precipitation of calcium oxalate is the reason for the toxicity of oxalates. Calcium oxalate may also occur in man, where it can appear as minute star-shaped crystals in the urine. It is the main constituent of the majority of urinary calculi in man (726,727). The relationships between dietary calcium... 

Whewellite CaC O - H O various plants Weddellite CaC O - 2H2O various plants Amorphous silica plants, grasses... 

Many mineral species are known to be selectively crystallized by the presence of bacteria. Carbonate minerals, such as calcite, aragonite, hydroxycalcite, and siderite oxide minerals, such as magnetite and todorokite oxalate minerals, such as whewellite and weddellite sulfide minerals, such as pyrite, sphalerite, wurtzite, greigite, and mackinawite and other minerals, such as jarosite, iron-jarosite, and g3q>sum, are known to precipitate in the presence of bacteria. Therefore, investigations have been developed to analyze the formation of banded iron ore by the action of bacteria, and to analyze the ancient environmental conditions of the Earth through the study of fossilized bacteria. 

In conclusion, any metal oxalate can be considered as a compound in a metastable equilibrium. The only sub-spontaneous diagenetic evolution of calcium oxalate is a possible transformation of weddellite into whewellite by dehydration (Frey-Wyssling, 1981 Verrecchia et al., 1993). Consequently, activation energy has to be provided for a complete oxidation of COM or COD, and life is the best and the most obvious candidate. Therefore, biogenic activity could be the key explanation for the absence of oxalate in paleosols as well as in the geological sedimentary record. 

Monje P. V. and Baran E. J. (1997) On the formation of whewellite in the cactaceae species Opuntia microdasys. Zeitschrift fuer Naturforshung (Section C) J. Biosci. 52(3-4), 267-269. 

Carbonates Phosphates Silica Calcite Aragonite Vaterite Monohydrocalcite Amorphous Dahllite Francolite Amorphous calcium phosphate hydrogel Amorphous ferric phosphate hydrogel Opal Iron oxides Sulfates Halides Oxalates Magnetite Goethite Lepidocrocite Amorphous hydrates Celestite Barite Gypsum Fluorite Weddellite Whewellite... 

The inorganic mineral oxalate (e.g. whewellite CaC204 H20) sometimes deposits on top of or underneath rock varnish. Because this mineral contains datable carbon, the radiocarbon age can provide a minimum age for the underlying or overlying varnish. The most reliable research on radiocarbon dating of oxalates in rock surface contexts has been conducted in west Texas (Rowe, 2000 Russ et al., 2000)... 

Concentrations of LMW organic acids are high enough in some soils that salts of the acids are precipitated. Weddellite and whewellite (hydrated calcium oxalate) have been observed as coatings on fungal hyphae in forest soils (67). Oxalate, often one of the more abundant of the identifiable LMW organic acids, significantly enhances oxide dissolution in laboratory studies (22, 23). 

Figure 2.4. Scanning electron micrographs showing crystalline deposition of (a) whewellite (< a( 2O4 H2O) and weddehte (CaC2O4-2H2O) and (h) moolooite (CuC2 O4 XH2O) on the filamentous mycehum of Serpula himantioides. (From E. P. Burford and G.M. Gadd, unpublished Burford et al., 2006).

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