Log InRegister
Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat Articles
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsThe ElementsUsersBooks & MagazinesMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery

IMA 2015-042 = hydroterskite

Posted by Marco E. Ciriotti  
Marco E. Ciriotti September 15, 2016 11:21AM
▪ Grice, J.D., Rowe, R., Poirier, G. (2015): Hydroterskite: A New Mineral Species From the Saint-Amable Sill, Quebec, and A Comparison With Terskite and Elpidite. Canadian Mineralogist, 53, 821-832.

Hydroterskite, ideally Na2ZrSi6O12(OH)6, is a new mineral species from the Saint-Amable sill at the Demix-Varennes quarry, near Varennes, Québec, Canada. Hydroterskite crystals are short prismatic in habit, up to 3 mm in width, and bounded by the {100}, {010}, and {001} prisms. The crystals are translucent, pale gray in color, with a white streak and vitreous luster. Hydroterskite is brittle and splintery, with good cleavages on the prismatic planes. It is biaxial negative, a = 1.562 ± 0.002, b = 1.567 ± 0.002, g = 1.571 ± 0.002, 2Vmeas. = 86(3)°, 2Vcalc. = 83°. Dispersion could not be observed, and there is no pleochroism. The optical orientation is X = c, Y = b, and Z = a. The average result of three analyses of a single grain (oxide wt.%) gave Na2O 7.82, K2O 0.07, CaO 0.62, FeO 0.89, MnO 0.71, Al2O3 0.08, La2O3 0.12, Ce2O3 0.24, SiO2 59.82, HfO2 0.11, ThO21.15, ZrO2 15.00, TiO2 1.15, Nb2O5 1.12, F 0.11, H2O (by stoichiometry) 8.79, for a total (–0.05 O=F) of 96.84. Magnesium, Y, Sr, and Cl were sought but not detected. The empirical formula on the basis of 18 anions with 6 OH– is (Na1.543K0.009Ca0.068La0.005Ce0.009)S1.634(Zr0.744Ti0.088Nb0.052Th0.005Hf0.003Fe0.076Mg0.002Mn0.061Al0.010)S1.041Si6.087O12(OH5.963F0.035Cl0.002)S6. The structure of hydroterskite is orthorhombic in the centric space group Pnca, with a 13.956(6), b 14.894(7), c 7.441(4) Å, V1546.8(2.0) Å3, and Z = 4. It has been refined to an R index of 0.036 on the basis of 1080 observed reflections. There are two crystallographically distinct Na sites, both with eight-fold co-ordination: [Na1O6(OH)2] is a hexagonal dipyramid polyhedron, whereas [Na2O6(OH)2] is a bifurcated pentagonal dipyramid. The Zr atom is in a regular octahedral coordination. Silicon, in tetrahedral coordination with oxygen, forms spiral chains parallel to the c axis. These chains are cross-linked by edge-sharing [ZrO6] octahedra and [NaO8] polyhedra. All three H atoms were located. The crystal-structure determination of terskite in the literature was most likely incorrectly assigned to an acentric space-group. The hydroterskite crystal structure is compared to the structures of terskite, elpidite, and yusupovite.
Knut Edvard Larsen September 24, 2016 01:30PM
Mineralpage updated
Sorry, only registered users may post in this forum.

Click here to login

Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Public Relations by Blytheweigh.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2019, except where stated. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: February 16, 2019 04:04:04
Go to top of page