Mapiquiroite, (Sr,Pb)(U,Y)Fe2(Ti,Fe3þ)18O38, was identified as a new mineral from the baryte þ pyrite þ iron oxide ores of Buca della Vena (BdV) and Monte Arsiccio (MA) mines, Apuan Alps, Tuscany, Italy. At BdV, mapiquiroite occurs as complex rhombohedral or tabular pseudo-hexagonal crystals, up to 1mmin size, black in colour, with a sub-metallic lustre, in quartzþ ‘adularia’ þ baryte veins embedded in schists, in association with allanite-(Ce), anatase, destinezite, gypsum, monazite-(Ce), pyrite, rutile, and ‘tourmaline’; atMA, mapiquiroite forms tabular pseudo-hexagonal crystals, up to 5mmin size, in quartzþcarbonate veins embedded in magnetite-rich dolostones, in association with baryte, boulangerite, derbylite, siderite, and sphalerite. Under the microscope, mapiquiroite is blackish in colour, weakly bireflectant, and non-pleochroic. Internal reflections are absent. Anisotropism is distinct, without characteristic rotation tints. Minimum and maximum reflectance data for COM wavelengths [l (nm), Rair (%); data for the specimens from BdV and MA, respectively] are: 471.1, 17.0/17.2 and 17.7/18.0; 548.3, 16.7/17.0 and 17.6/17.8; 586.6, 16.4/16.7 and 17.3/17.7; 652.3, 16.1/16.3 and 17.0/17.3. Vickers hardness is 750 kg mm2 and 782 kgmm2 for specimens from BdV and MA, respectively, corresponding to a Mohs’ hardness 6. The chemical data point to the formulae (Sr0.533La0.176Pb0.105Na0.030Ca0.026)¼0.870(U0.407Ce0.101Y0.205Mn0.072)¼0.785 Fe3þ2.000 (Ti12.423Fe3þ3.345Cr1.624V5þ 0.129Al0.032Sn0.013Nb0.007)¼17.573O38 (BdV) and (Sr0.312Pb0.248Na0.019Ca0.014La0.009)¼0.602(U0.858Y0.070Ce0.021Mn0.005)¼0.954(Fe3þ1.695Zn0.305)¼2.000(Ti12.070Fe3þ 4.987V5þ0.372Al0.030Nb0.030Cr0.015Sn0.001)¼17.505O38 (MA).Mapiquiroite is trigonal, R3,with a 10.3719(7), c 20.875(1)A ° , V 1944.8(2)A ° 3 and a 10.3854(3), c 20.8942(6) A ° , V 1951.7(1) A ° 3 for the specimens from BdV and MA, respectively. The crystal structures of mapiquiroite from these two occurrences were refined to R1 ¼ 0.028 and 0.032, respectively. Mapiquiroite is isostructural with other members of the crichtonite group. The name mapiquiroite honours four Italian mineral collectors, Riccardo Mazzanti, Luigi Pierotti, Ugo Quilici, and Moreno Romani for their contribution to the study of the mineralogy of baryte þ pyrite þ iron oxide deposits from the Apuan Alps.
|Autori interni:||BIAGIONI, CRISTIAN|
|Autori:||BIAGIONI C.; ORLANDI P; PASERO M.; NESTOLA F.; BINDI L.|
|Titolo:||Mapiquiroite, (Sr,Pb)(U,Y)Fe2(Ti,Fe3+)18O38, a new member of the crichtonite group from Apuan Alps, Tuscany, Italy.|
|Anno del prodotto:||2014|
|Digital Object Identifier (DOI):||10.1127/0935-1221/2014/0026-2382|
|Appare nelle tipologie:||1.1 Articolo in rivista|