Weddellite from renal stones: Structure refinement and dependence of crystal chemical features on H2O content

The Great Barrier Reef Expedition 1928–29: The crystal structure and occurrence of weddellite, ideally CaC2O4·2.5H2O, from the Low Isles, Queensland

“…The crystal structure of weddellite from the Low Isles is consistent with the structures reported by Tazzoli and Domeneghetti (1980) and Izatulina et al (2014), and is dominated by distorted CaO 8 square antiprisms, which share edges with two neighbouring polyhedra to form infinite chains along [001]. Four of the oxygen ligands of the Ca polyhedron are from bidentate oxalate anions, two from monodentate oxalate groups, and the remaining two are nonzeolitic water oxygen atoms OW1 and OW2.…”

“…There is no evidence that the zeolitic water site OW3 is split, as was the case for Izatulina et al (2014); however, an additional low-occupancy water O site was located at the origin (Table 2). Tazzoli and Domeneghetti (1980) had earlier discounted the [0;0;0] site as a (2) 0.0068 (2) 0.0046 (2) 0 0 -0.00075 (13) O1 0.25412(10) 1.14378 (9) 0.68362 (17) (6) 0.0082 (6) 0.0011 (5) 0.0059 (6) 0.0036 (6) OW2 0 0.0118 (7) 0.0112 (7) 0.0060 (7) -0.0001 (5) 0.0007 (5) 0.0004 (5) OW3 ½ possibility for hosting water, purely because the distance from OW3 would be a physically unrealistic 2.35 Å.…”

“…Sterling (1965) originally postulated that x could not be more than 0.5, based on the multiplicity of the OW3 site, while the crystal studied by Tazzoli and Domeneghetti (1980) had an x of 0.37 and showed a split water O site with an OW3-OW30 distance of ∼0.56 Å. The crystals studied by Izatulina et al (2014) had x in the range 0.13-0.37 and showed the same split water O site, with an OW3-OW31 distance of ∼0.6 Å.…”

Vibrational Signatures of Calcium Oxalate Polyhydrates

“…Based on the refinements of the structures of kidney stones by Izatulina et al . and by Tazzoli and Domenegetti, Izatulina et al . estimated an x value ranging from 0.13 to 0.37.…”

Calcium Oxalates in Lichens on Surface of Apatite-Nepheline Ore (Kola Peninsula, Russia)

“…The closeness of phase composition and morphology of the calcium oxalate crystals formed on apatite ore and carbonate rocks (marbles and limestones) suggests that the presence of CO 3 2− and PO 4 3− anions in the crystallization medium does not or almost does not affect the morphogenetic features of the calcium oxalate formation in the lichen thallus. In both cases, formation of whewellite and weddellite (which is regarded as metastable in the field of whewellite) can be explained by the significant concentration of Ca 2+ ions in the solution, which come mainly from the underlying fluorapatite rock, and by the presence of a number of inorganic and organic impurities [37,39,40] that incorporate into the crystallization medium from the apatite substrate and, together with metabolic products of microorganisms, that present in biofilms. It can be assumed that Sr 2+ and other admixture ions which predominantly incorporate into weddellite are among the impurities that contribute to its stabilization on the surface of the apatite-nepheline rock.…”