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, Poços de Caldas Massif, Minas Gerais, Brazil
Author:
Day Maxwell C.1, Sokolova Elena1, Hawthorne Frank C.1, Horváth László2, Pfenninger-Horváth Elsa2
Affiliation:
1. Department of Earth Sciences, University of Manitoba, 125 Dysart Road, Winnipeg, Manitoba R3T 2N2, Canada 2. 594 Main Road, Hudson Heights, Quebec J0P1J0, Canada
Abstract
ABSTRACT
Bortolanite (IMA 2021–040a), ideally Ca2(Ca1.5Zr0.5)Na(NaCa)Ti(Si2O7)2(FO)F2, is a rinkite-group (seidozerite supergroup) TS-block mineral from Poços de Caldas massif, Minas Gerais, Brazil. Associated minerals are götzenite, nepheline, alkali feldspar, aegirine, natrolite, analcime, and manganoan pectolite. Bortolanite shows complex compositional zoning with götzenite and is visually indistinguishable from götzenite. 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). Dcalc. = 3.195 g/cm3. Bortolanite is biaxial (+) with refractive indices (λ = 589.3 nm) α = 1.673(2), β = 1.677(2), γ = 1.690(2); 2Vmeas. = 56(2)°, 2Vcalc. = 58.4°. 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)Σ2[Ca1.56(Zr0.41Hf0.01Y0.02)Σ0.44]Σ2(Na0.85Ca0.15)Σ1(Na1.18Ca0.60Mn0.16Fe2+0.06)Σ2(Ti0.94Nb0.06)Σ1(Si4.07O14)(O1.24F0.76)Σ2F2, Z = 1. The simplified formula is Ca2(Ca,Zr)2Na(Na,Ca)2Ti(Si2O7)2(O,F)2F2. Bortolanite is triclinic, space group P, a 9.615(3), b 5.725(2), c 7.316(2) Å, α 89.91(1), β 101.14(1), γ 100.91(1)°, V 387.7(3) Å3. The crystal structure was refined to R1 = 3.19% on the basis of 2194 unique reflections [F > 4σ(F)] measured using a Bruker APEX II ULTRA three-circle diffractometer with a rotating-anode generator (MoKα), 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 TS block 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 MO(1) octahedra, [8]Na-dominant MO(2) polyhedra and (Na,Ca) MO(3) octahedra. In the H sheet in bortolanite, Si2O7 groups link to (Ca1.5Zr0.5) MH and Ca-dominant AP octahedra. Along a, TS blocks link directly through common edges of MH and AP polyhedra and common vertices of MH, AP, and Si polyhedra of the H sheets belonging to two TS blocks. The name bortolanite is after the locality: the Bortolan quarry in the Poços de Caldas massif, Brazil. Bortolanite is isostructural with three rinkite-group minerals: fogoite-(Y), hainite-(Y), and götzenite.
Publisher
Mineralogical Association of Canada
Subject
Geochemistry and Petrology
Reference33 articles.
1. Anthony,
J.W.,
Bideaux,
R.A.,
Bladh,
K.W.,
&
Nichols,M.C.
(1995)
Handbook of Mineralogy. Silica, Silicates
.
Mineral Data Publishing, Tucson, Volume 2(1),p.309. 2. Atencio,
D.,
Coutinho,
J.M.V.,
Ulbrich,
M.N.C.,
Vlach,
S.R.F.,
Rastsvetaeva,
R.K.,
&
Pushcharovsky,D.Yu.
(1999)
Hainite from Poços de Caldas, Minas Gerais, Brazil.
Canadian Mineralogist37,
91–98. 3. Blumrich,
J.
(1893)
Die Phonolithe des Friedländer Bexirkes in Nordböhmen.
Tschermaks Mineralogische und Petrographische Mitteilungen13,
465–495. 4. Brown,
I.D.
(1981)
The bond valence method: An empirical approach to chemical structure and bonding.
InStructure and Bonding in Crystals II (
O'KeeffeM. &
Navrotsky,A.eds.).Academic Press,
New York, N.Y.
(1–30). 5. Brögger,
W.C.
(1887)
Forelöbig meddelelse om mineralerne på de sydnorske augit- og nefelinsyeniters grovkornige gange.
Geologiska Föreningens i Stockholm Förhandlingar109(4),
247–274.
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