Abstract
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)Σ=1.04 (Y0.62U0.18Yb0.09Sc0.08)Σ=0.97 Fe22+(Ti12.66Fe4.783+V0.263+)Σ=17.70O38 and unit-cell parameters a = 10.376(3) Å, c = 20.903(6) Å, and V = 1949(1) Å3.
Highlights
“Mohsite” was first cited in 1827 by Levy [1] in rock samples from the Dauphineregion (France)
“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
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)Σ=1.04(Y0.62U0.18Yb0.09Sc0.08)Σ=0.97 Fe22+(Ti12.66Fe34+.78V30+.26)Σ=17.70O38 and unit-cell parameters a = 10.376(3) A, c = 20.903(6) A, and V = 1949(1) A 3
Summary
“Mohsite” was first cited in 1827 by Levy [1] in rock samples from the Dauphineregion (France). 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 new Ca-rich member of the crichtonite supergroup, which was named loveringite by Gatehouse et al [7]. These authors stated that the name “mohsite” was incorrectly used for a member of the crichtonite-senaite series, they proposed to discredit the name “mohsite,” and IMA accepted the proposal
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