Kazanskyite, Ba & TiNbNa 3Ti(Si 2O 7) 2O 2(OH) 2(H 2O) 4, a Group-III Ti-disilicate mineral from the Khibiny alkaline massif, Kola Peninsula, Russia : description and crystal structure

• Published in: Mineralogical Magazine
• Main Authors: F. Cámara, E. Sokolova, F. C. Hawthorne
• Other Authors: F.C. Hawthorne
• Format: Article in Journal/Newspaper
• Language: English
• Published: Mineralogical Society of Great Britain 2012
• Subjects: crystal structure; Group III; kazanskyite; Khibiny alkaline massif; Kola Peninsula; new mineral; Russia; Ti-disilicate; TS block; Settore GEO/06 - Mineralogia; Khibiny; Kukisvumchorr; kola peninsula
• Online Access: http://hdl.handle.net/2434/474904; https://doi.org/10.1180/minmag.2012.076.3.03

Kazanskyite, Ba&TiNbNa 3Ti(Si 2O 7) 2O 2(OH) 2(H 2O) 4, is a Group-III TS-block mineral from the Kirovskii mine, Mount Kukisvumchorr, Khibiny alkaline massif, Kola Peninsula, Russia. The mineral occurs as flexible and commonly bent flakes 2-15 μm thick and up to 330 μm across. It is colourless to pale tan, with a white streak and a vitreous lustre. The mineral formed in a pegmatite as a result of hydrothermal activity. Associated minerals are natrolite, barytolamprophyllite, nechelyustovite, hydroxylapatite, belovite-(La), belovite-(Ce), gaidonnayite, nenadkevichite, epididymite, apophyllite-(KF) and sphalerite. Kazanskyite has perfect cleavage on 001, splintery fracture and a Mohs hardness of 3. Its calculated density is 2.930 g cm -3. Kazanskyite is biaxial positive with α 1.695, β 1.703, γ 1.733 (λ590 nm), 2V meas = 64.8(7)°, 2V calc = 55.4°, with no discernible dispersion. It is not pleochroic. Kazanskyite is triclinic, space group P1, a 5.4260(9), b 7.135(1), c 25.514(4) Å, α 90.172(4), β 90.916(4), γ 89.964(3)°, V 977.61(3) Å 3. The strongest lines in the X-ray powder-diffraction pattern [d(Å)(I)(hkl)] are: 2.813(100)(124,122), 2.149(82)(222,220,207,220,222), 3.938(70)(113,112), 4.288(44)(111,110,110,111), 2.128(44)(223,221,134,221,134,221,223), 3.127(39)(116,115), 3.690(36)(114), 2.895(33)(123,121) and 2.955(32)(120,120,122). Chemical analysis by electron microprobe gave Nb 2O 59.70, TiO 219.41, SiO 228.21, Al 2O 30.13, FeO 0.28, MnO 4.65, BaO 12.50, SrO 3.41, CaO 0.89, K 2O 1.12, Na 2O 9.15, H 2O 9.87, F 1.29, O = F-0.54, sum 100.07 wt.%; H 2O was determined from structure refinement. The empirical formula is (Na 2.55Mn 0.31Ca 0.11Fe 2+0.03) Σ3(Ba 0.70Sr 0.28K 0.21Ca 0.03) Σ1.22(Ti 2.09Nb 0.63Mn 0.26Al 0.02) Σ3Si 4.05O 21.42H 9.45F 0.59, calculated on 22 (O + F) a.p.f.u., Z = 2. The structural formula of the form A P2M H2M O4(Si 2O 7) 2X O4X PMX PA(H 2O) n is (Ba 0.56Sr 0.22K 0.15Ca 0.03& 0.04) Σ1(& 0.74Ba 0.14Sr 0.06K 0.06) Σ1(Ti 0.98Al 0.0 2) Σ1(Nb 0.63Ti 0.37) Σ1(Na 2.55Mn 0.31Ca 0.11Fe ...