BORTOLANITE, Ca2(Ca1.5Zr0.5)Na(NaCa)Ti(Si2O7)2(FO)F2, A NEW RINKITE-GROUP (SEIDOZERITE SUPERGROUP) TS-BLOCK MINERAL FROM THE BORTOLAN QUARRY, POCOS DE CALDAS MASSIF, MINAS GERAIS, BRAZIL

Bortolanite (IMA 2021-040a), ideally Ca-2(Ca1.5Zr0.5)Na(NaCa)Ti(Si2O7)(2)(FO)F-2, is a rinkite-group (seidozerite supergroup) TS-block mineral from Pocos de Caldas massif, Minas Gerais, Brazil. Associated minerals are gotzenite, nepheline, alkali feldspar, aegirine, natrolite, analcime, and manganoan pectolite. Bortolanite shows complex compositional zoning with gotzenite and is visually indistinguishable from gotzenite. Bortolanite is pale-yellow to brown and has a vitreous luster. Cleavage is perfect parallel to {100}. Mohs hardness is 5. Bortolanite fluoresces weak yellow under ultraviolet light (100-280 nm). D-calc. = 3.195 g/cm(3). Bortolanite is biaxial (+) with refractive indices (lambda = 589.3 nm) alpha = 1.673(2), beta = 1.677(2), gamma = 1.690(2); 2V(meas.) = 56(2)degrees, 2V(calc.) = 58.4 degrees. Chemical analysis by electron microprobe gave Nb2O5 1.07, HfO2 0.20, ZrO2 6.70, TiO2 9.94, SiO2 32.49, Gd2O3 0.12, Nd2O3 0.37, Ce2O3 1.25, La2O3 0.65, Y2O3 0.31, FeO 0.59, MnO 1.46, CaO 31.15, Na2O 8.36, F 6.95, O=F -2.93, sum 98.68 wt.%. The empirical formula based on 18 (O + F) apfu is (Ca1.88La0.03Ce0.06Nd0.02Gd0.01)(Sigma 2)[Ca-1.56(Zr0.41Hf0.01Y0.02)(Sigma 0.44)](Sigma 2)(Na0.85Ca0.15)(Sigma 1)(Na1.18Ca0.60Mn0.16Fe0.062+)(Sigma 2)(Ti0.94Nb0.06)(Sigma 1)(Si4.07O14)(O1.24F0.76)(Sigma 2)F-2, Z = 1. The simplified formula is Ca-2(Ca,Zr)(2)Na(Na,Ca)(2)Ti(Si2O7)(2)(O,F)(2)F-2. Bortolanite is triclinic, space group P (1) over bar, a 9.615(3), b 5.725(2), c 7.316(2) angstrom, alpha 89.91( 1), beta 101.14(1), gamma 100.91(1)degrees, V 387.7( 3) angstrom(3). The crystal structure was refined to R-1 = 3.19% on the basis of 2194 unique reflections [F > 4 sigma(F)] measured using a Bruker APEX II ULTRA three-circle diffractometer with a rotating-anode generator (MoK alpha), multilayer optics, and an APEX II 4K CCD detector.The crystal structure of bortolanite is a framework of TS (Titanium-Silicate) blocks [structure type B3(RG)], where the TSblock consists of HOH sheets (H-heteropolyhedral, O-octahedral). The TS block exhibits linkage and stereochemistry typical for the rinkite group where Ti (+ Nb + Zr) = 1 apfu. The O sheet is composed of Ti-dominant M-O (1) octahedra, Na-[8]-dominant M-O(2) polyhedra and (Na,Ca) M-O(3) octahedra. In the H sheet in bortolanite, Si2O7 groups link to (Ca1.5Zr0.5) M-H and Ca-dominant AP octahedra. Along a, TS blocks link directly through common edges of M-H and A(P) polyhedra and common vertices of M-H, A(P), and Si polyhedra of the H sheets belonging to two TS blocks. The name bortolanite is after thelocality: the Bortolan quarry in the Pocos de Caldas massif, Brazil. Bortolanite is isostructural with three rinkite-groupminerals: fogoite-( Y), hainite-( Y), and gotzenite.