%0 Journal Article
%T ¡°Mohsite¡± of Colomba: Identification as Dessauite-(Y)
%A Erica Bittarello
%A Marco E. Ciriotti
%A Emanuele Costa
%A Lorenzo Mariano Gallo
%J International Journal of Mineralogy
%D 2014
%R 10.1155/2014/287069
%X During a reorganization of the mineralogical collection of Turin University, old samples of the so-called mohsite of Colomba were found. ¡°Mohsite¡± was discredited in 1979 by Kelly et al., as a result of some analyses performed on the equivalent material coming from the French region of Hautes-Alpes, but the original samples found in similar geological setting in Italy were lost and never analysed with modern equipment. After more than a century, the rediscovered samples of Professor Colomba were analysed by means of SEM-EDS analysis, microRaman spectroscopy, and X-ray diffraction. The results have demonstrated that the historical samples studied by Colomba are Pb-free dessauite-(Y), and pointed to an idealized crystal chemical formula (Sr0.70Na0.25Ca0.09)¦²=1.04 (Y0.62U0.18Yb0.09Sc0.08)¦²=0.97£¿£¿ (Ti12.66 )¦²=17.70O38 and unit-cell parameters a = 10.376(3)£¿£¿, c = 20.903(6)£¿£¿, and V = 1949(1)£¿£¿3. 1. Introduction ¡°Mohsite¡± was first cited in 1827 by L¨¦vy [1] in rock samples from the Dauphin¨¦ region (France). The identification was obtained mainly on morphological evidence, but the original samples studied by L¨¦vy were lost, and no other analysis could be made for a better identification. In 1901, Lacroix [2] acquired some samples coming from Le Plate Muratouse, La Grave area, at the Department of Hautes-Alpes (Provence-Alpes-C£¿te d¡¯Azur, France). Based only on the morphological features, very similar to those described by L¨¦vy, and considering the close topographical occurrence, Lacroix identified these samples as ¡°mohsite¡± and, since the old types were missing, the new samples became neotypes. One year later, Colomba [3], at that time, Professor of Mineralogy at the Royal University and Director of the Mineralogical Museum of Turin (Piedmont, Italy), described morphologically similar small crystals coming from La Beaume, Oulx (Susa Valley, Piedmont, Italy) not so far from the French occurrence and in a comparable geological and mineralogical context (Colomba, [3]). Chemical qualitative analysis carried out by Colomba showed only the presence of TiO, CaO, FeO, and minor MgO. The data of Colomba were later summarized by Zambonini [4]. These samples (few millimetric size crystals) were lost in some drawer of the University Museum Warehouse and forgotten for about a century (Costa and Gallo, [5]). Kelly et al. [6] reported that they had obtained some of the samples of the Lacroix collection and gave additional data on them. The analysis performed by Kelly showed the presence of Sr and minor Pb, but not calcium, so the mineral of Lacroix and Colomba was not the
%U http://www.hindawi.com/journals/ijm/2014/287069/