A single-crystal neutron and X-ray diffraction study of pezzottaite, Cs(Be2Li)Al2Si6O18

作者：Gatta G Diego^*; Adamo Ilaria; Meven Martin; Lambruschi Erica

来源：Physics and Chemistry of Minerals, 2012, 39(10): 829-840.

DOI：10.1007/s00269-012-0539-3

• Pezzottaite
• Single-crystal X-ray and neutron diffraction
• Microprobe analysis
• Infrared spectroscopy

The chemical composition and the crystal structure of pezzottaite [ideal composition Cs(Be2Li)Al2Si6O18; space group: R (3) over barc, a = 15.9615(6) angstrom, c = 27.8568(9) angstrom] from the type locality in Ambatovita (central Madagascar) were investigated by electron microprobe analysis in wavelength dispersive mode, thermo-gravimetric analysis, Fourier-transform infrared spectroscopy, single-crystal X-ray (at 298 K) and neutron (at 2.3 K) diffraction. The average chemical formula of the sample of pezzottaite resulted (Cs1,Cs2)(Cs0.565Rb0.027K0.017)(Sigma 0.600)(Na1,Na2)(Na0.101Ca0.024)(Sigma 0.125)Be2.078Li0.922 (Al1,Al2)(Mg0.002Mn0.002Fe0.003Al1.978)(Sigma 1.985) (Si1,Si2,Si3)(Al0.056Si5.944)(Sigma 6)O-18 center dot 0.27H(2)O. The (unpolarized) IR spectrum over the region 3,800-600 cm(-1) was collected and a comparison with the absorption bands found in beryl carried out. In particular, two-weak absorption bands ascribable to the fundamental H2O stretching vibrations (i.e. 3,591 and 3,545 cm(-1)) were observed, despite the mineral being nominally anhydrous. The X-ray and neutron structure refinements showed: (a) a non-significant presence of aluminium, beryllium or lithium at the S

• 出版日期2012-11