Original paper
Caoxite, Ca(H2O)3 (C2O4), a new mineral from the Cerchiara mine, northern Apennines, Italy
Basso, R.; Lucchetti, G.; Zefiro, L.; Palenzona, A.
Neues Jahrbuch für Mineralogie - Monatshefte Jg. 1997 Heft 2 (1997), p. 84 - 96
24 references
published: Apr 15, 1997
DOI: 10.1127/njmm/1997/1997/84
ArtNo. ESP156199702002, Price: 29.00 €
Abstract
Caoxite has been found in the Cerchiara mine, Val di Vara, northern Apennines, Italy. It occurs, together with the associated minerals barite, quartz and an unidentified Mn oxide, in small veins cutting Mn-Ba-mineralized cherts. Caoxite, appearing commonly both as isolated and spherulitic aggregates of elongated stocky tabular on {010} crystals, is colourless, transparent, optically biaxial negative and nonpleochroic. Microprobe analyses reveal a homogeneous and quasi-ideal content of calcium, the only detectable element. The strongest lines in the powder pattern are d100+011 = 5.52 Å and d210 = 2.834 Å. The crystal structure, described in the space group PῙ with a = 6.097(1) Å, b = 7.145(1) Å, c = 8.434(1) Å, α = 76.54(1)°, β = 70.30 (1)°, γ = 70.75(1)° and Z = 2, has been refined to R = 0.036, confirming the new mineral to be the natural analogue of the already known synthetic calcium oxalate trihydrate. A comparison with the structures of whewellite and weddelite is outlined.
Keywords
Caoxite • new mineral • physical and chemical data • powder pattern • structure refinement