A new anhydrous amphibole from the Hoskins Mine, Grenfell, New South Wales, Australia; description and crystal structure of ungarettiite, NaNa₂(Mn (super 2+)₂Mn (super 3+)₃)Si₈O₂₂O₂

Abstract

Other| February 01, 1995 A new anhydrous amphibole from the Hoskins Mine, Grenfell, New South Wales, Australia: Description and crystal structure of ungarettiite, NaNa2(Mn22+Mn33+)Si8O22O2 Frank C. Hawthorne; Frank C. Hawthorne CNR Centro di Studio per la Cristallochimica e la Cristallografia, Pavia, Italy Search for other works by this author on: GSW Google Scholar Roberta Oberti; Roberta Oberti Search for other works by this author on: GSW Google Scholar Elio Cannillo; Elio Cannillo Search for other works by this author on: GSW Google Scholar Nicola Sardone; Nicola Sardone Search for other works by this author on: GSW Google Scholar Alberto Zanetti; Alberto Zanetti Search for other works by this author on: GSW Google Scholar Joel D. Grice; Joel D. Grice Search for other works by this author on: GSW Google Scholar Paul M. Ashley Paul M. Ashley Search for other works by this author on: GSW Google Scholar American Mineralogist (1995) 80 (1-2): 165–172. https://doi.org/10.2138/am-1995-1-216 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Frank C. Hawthorne, Roberta Oberti, Elio Cannillo, Nicola Sardone, Alberto Zanetti, Joel D. Grice, Paul M. Ashley; A new anhydrous amphibole from the Hoskins Mine, Grenfell, New South Wales, Australia: Description and crystal structure of ungarettiite, NaNa2(Mn22+Mn33+)Si8O22O2. American Mineralogist 1995;; 80 (1-2): 165–172. doi: https://doi.org/10.2138/am-1995-1-216 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Ungarettiite is a new amphibole species from the Hoskins mine, near Grenfell, New South Wales, Australia. It occurs with Mn-bearing oxides, silicates, and carbonates in a stratiform schist associated with metajasper, metabasalt, and metasiltstone. Ungarettiite is brittle, H = 6, Dmeas = 3.52 g/cm3, Dcalc = 3.45 g/cm3. In plane-polarized light, it is strongly pleochroic, X = orange red, Y ~ Z = very dark red; X ∧ a = − 2° (in β acute), Y = b, Z ∧ c = 17° (in β obtuse), with absorption X < Y ≤ Z. Ungarettiite is biaxial positive, α = 1.717(2), β = 1.780(4), γ = 1.800(2); 2V = 51(2)°, dispersion r < v. Ungarettiite is monoclinic, space group C2/m, a = 9.89(2), b = 18.04(3), c = 5.29(1) Å, β = 104.6(2)°, V = 912(1) Å3, Z = 2. The strongest ten X-ray diffraction lines in the powder pattern are [d(I, hkl)]: 2.176(10,171), 3.146(9,310), 2.544(9,202), 1.447(9,3.11.1), 3.400(8,131), 1.656(8,461), 8.522(7,110), 2.299(7,171), 2.575(6,241), and 2.047(6,202). Analysis by a combination of electron microprobe and crystal-structure refinement gives SiO2 50.66, Al2O3 0.04, TiO2 0.03, Fe2O3 0.50, FeO 0.00, Mn2O3 24.35, MnO 12.42, MgO 1.46, ZnO 0.10, CaO 0.18, Na2O 9.13, K2O 0.76, F not detected, sum 99.63 wt%. The formula unit calculated on the basis of 24 O atoms is (K0.15Na0.82)(Na1.97Ca0.03)(Mn1.662+Mg0.34Mn2.963+Fe0.063+Zn0.01)(Si7.99Al0.01)O22O2 and is close to the ideal end-member composition of NaNa2(Mn22+Mn33+)Si8O22O2⁠.The crystal structure of ungarettiite was refined to an R index of ~1.5% using MoKα X-ray intensity data. Site-scattering refinement shows that the M1, M2, and M3 sites are occupied dominantly by Mn. The 〈M-O〉 distances are M1: 2.03; M2: 2.17; M3: 2.01 Å, compatible with the site occupancies M1 ~ M3 ~ Mn3+, M2 ~ Mn2+. All bonds to the O3 anion are very short, and a bond valence analysis indicates that the O3 site is occupied by a divalent anion: O2−, as suggested by the overall electroneutrality requirement of the structural formula. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.