Kolskyite, (Ca)Na2Ti4(Si2O7)2O4(H2O)7, a group-IV Ti-disilicate mineral from the Khibiny Alkaline Massif, Kola Peninsula, Russia: description and crystal structure.

• Published in: The Canadian Mineralogist
• Main Authors: CAMARA ARTIGAS, Fernando, Sokolova E, Abdu Y, Hawthorne FC, Khomyakov AP
• Other Authors: Cámara F
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2013
• Subjects: kolskyite; new mineral; Khibiny alkaline massif; Kola Peninsula; Russia; crystal structure; Group IV; Ti-disilicate; TS-block; kola peninsula
• Online Access: http://hdl.handle.net/2318/147208; https://doi.org/10.3749/canmin.51.6.921; http://www.mineralogicalassociation.ca/template/EJournal/

Kolskyite (Ca square)Na2Ti4(Si2O7)(2)O-4(H2O)(7), is a Group-IV TS-block mineral from the Kirovskii mine, Mount Kukisvumchorr, Khibiny alkaline massif, Kola Peninsula, Russia. The mineral occurs as single, platy crystals 2-40 mu m thick and up to 500 mu m across. It is pinkish yellow, with a white streak and a vitreous luster. The mineral formed in a pegmatite as a result of hydrothermal activity. Associated minerals are natrolite, nechelyustovite, kazanskyite, barytolamprophyllite, hydroxylapatite, belovite-(La), belovite-(Ce), gaidonnayite, nenadkevichite, epididymite, apophyllite-(KF), and sphalerite. Kolskyite has perfect cleavage on {001}, splintery fracture, and a Mohs hardness of 3. Its calculated density is 2.509 g/cm(3). Kolskyite is biaxial negative with alpha 1.669, beta 1.701, gamma 1.720 (lambda 590 nm), 2V(meas.) = 73.6(5)degrees, 2V(calc.) = 74.0 degrees, with no discernible dispersion. It is nonpleochroic. Kolskyite is triclinic, space group P (1) over bar, a 5.387(1), b 7.091(1), c 15.473(3) angstrom, alpha 96.580(4), beta 93.948(4), gamma 89.818(3)degrees, V 585.8(3) angstrom(3). The strongest lines in the X-ray powder-diffraction pattern [d(angstrom)(I)(hkl)] are: 15.161(100)(001), 2.810(19)(121, 1 (2) over bar2), 3.069(12) (005), 2.938(10)(((1) over bar(2) over bar1,120, 1 (2) over bar1), 2.680(9)(((1) over bar(2) over bar3,200,114, (2) over bar 01), 1.771(9) (0 (4) over bar1,040), 2.618(8)(1 (2) over bar3,122), 2.062(7)(221,2 (2) over bar2, (2) over bar(2) over bar3,(2) over bar 22), and 1.600(7)((3) over bar(2) over bar1,(3) over bar 20,320). Chemical analysis by electron microprobe gave Nb2O5 6.96, ZrO2 0.12, TiO2 26.38, SiO2 27.08, FeO 0.83, MnO 2.95, MgO 0.76, BaO 3.20, SrO 5.21, CaO 4.41, K2O 0.79, Na2O 6.75, H2O 13.81, F 0.70, O = F -0.29, sum 99.66 wt.%; H2O was determined from structure solution and refinement. The empirical formula was calculated on 25 (O + F) apfu: (Na1.93Mn0.04Ca0.03)(Sigma 2)(Ca0.67Sr0.45Ba0.19K0.15)(Sigma 1.46)(Ti2.93Nb0.46Mn0.33Mg0.17Fe2+ Zr-0.10(0.01))(Sigma ...