Suseinargiuite, (Na (sub 0.5) Bi (sub 0.5) )MoO (sub 4) , the Na-Bi analogue of wulfenite, from Su Seinargiu, Sardinia, Italy
Suseinargiuite, (Na (sub 0.5) Bi (sub 0.5) )MoO (sub 4) , the Na-Bi analogue of wulfenite, from Su Seinargiu, Sardinia, Italy
European Journal of Mineralogy (July 2015) 27 (5): 695-699
- cell dimensions
- chemical composition
- crystal chemistry
- crystal structure
- crystal zoning
- electron probe data
- Europe
- formula
- Italy
- mineral data
- molybdates
- new minerals
- optical properties
- Raman spectra
- Sardinia Italy
- solid solution
- Southern Europe
- spectra
- wulfenite
- X-ray diffraction data
- Sarroch Italy
- Cagliari Italy
- suseinargiuite
- Su Seinargiu
The new mineral species suseinargiuite, (Na (sub 0.5) Bi (sub 0.5) )MoO (sub 4) , has been discovered in the Mo-Bi occurrence of Su Seinargiu, Sarroch, Cagliari, Sardinia, Italy. It occurs as hemispherical aggregates of very small acicular crystals, up to some micrometres in length. It is colourless, with a pearly to adamantine lustre. In the studied specimens, suseinargiuite is associated with wulfenite. Micro-Raman spectra were collected in the region between 100 and 2000 cm (super -1) . The following bands have been observed (in cm (super -1) ): 131, 188, 319, approximately 376, approximately 772, and 876. Electron microprobe data collected on a chemically zoned grain gave (outer and inner zone, respectively - in wt%): MoO (sub 3) 49.03, Bi (sub 2) O (sub 3) 42.97, PbO 2.89, Na (sub 2) O 3.69, total 98.58, and MoO (sub 3) 45.59, Bi (sub 2) O (sub 3) 34.47, PbO 12.04, Na (sub 2) O 3.03, total 95.13. On the basis of 4 O atoms per formula unit, the relevant chemical formulae are (Na (sub 0.35) Bi (sub 0.54) Pb (sub 0.04) ) (sub Sigma =0.93) Mo (sub 0.99) O (sub 4) and (Na (sub 0.31) Bi (sub 0.46) Pb (sub 0.17) ) (sub Sigma =0.94) Mo (sub 0.99) O (sub 4) , respectively. Main diffraction lines are [d in Aa (relative intensity) hkl]: 3.146 (100) 112, 2.912 (13) 004, 2.652 (18) 200, 1.964 (34) 204, 1.875 (15) 220, 1.728 (19) 116, and 1.616 (28) 312 and 132. Unit-cell parameters, refined from the powder X-ray diffraction data in a tetragonal setting, space group I4 (sub 1) /a, are a = 5.296(1), c = 11.673(2)Aa, V = 327.4(1)Aa (super 3) , Z = 4. Owing to the lack of suitable crystals and the very small amount of available material, the crystal structure of suseinargiuite was not solved. However, X-ray powder diffraction data, micro-Raman spectra, as well as chemical analysis, show the close correspondence between suseinargiuite with synthetic (Na (sub 0.5) Bi (sub 0.5) )MoO (sub 4) , which displays a scheelite-type structure.
