Pertlikite, a new tetragonal Mg-rich member of the voltaite group from Madeni Zakh, Iran
- Author(s)
- Andreas Ertl, John M. Hughes, Ruth C. Peterson, M. Darby Dyar
- Abstract
Pertlikite, a new member of the voltaite group, is the tetragonal Mg-dominant analog of the isometric phases voltaite and zincovoltaite. At its type locality, Madeni Zakh, Iran, the mineral occurs in a pyrite-bearing trachytic eruptive rock, and probably formed after the decompn. of pyrite. Pertlikite forms single crystals up to 1 cm; the phase is assocd. with metavoltine, botryogen, pyrite and alunite. In contrast to voltaite and zincovoltaite, the optical properties and the single-crystal study of the structure (R1 = 0.022) confirm the tetragonal symmetry, .omega. = 1.590(2), .epsilon. = 1.586(2), space group 141/acd, a 19.2080(3), c 27.2158(7) .ANG., V 10041.2(6) .ANG.3, and Z = 8. The results of the chem. anal., in combination with the Moessbauer data and the crystal-structure refinement, give the formula (K1.98Na0.01)1.99 M2(Fe2+1.13Mg0.49Mn2+0.27Fe3+0.10Zn0.01)2.00 M3(Mg2.52Fe3+1.49)4.01 M1Fe3+2.00Al1.00(SO4)12.00.bul.18 H2O, which can be simplified to an ideal formula: K2 M2(Fe2+,Mg)2 M3(Mg,Fe3+)4 M1Fe3+2Al (SO4)12.bul.18 H2O. The strongest eight lines of the powder pattern [d in A(I)(hkl)] are: 5.543(28)(132), 3.396(100)(440), 3.136(21)(345), 3.038(39)(444), 2.848(31)(361), 2.534(21)(273), 2.078(29)(567) and 1.601(21)(6104). The unit-cell parameters refined from the powder data (CuK.alpha. radiation) are a 19.2167(2), c 27.1976(4) .ANG.. The tetragonal structure of pertlikite results from Mg,Fe order at the Fe2 site. Relative to the isometric voltaite and zincovoltaite, the Fe2 site splits to create a site that is predominantly Mg (Mg3) and another that is dominantly Fe (Fe2) in pertlikite. For the three metal sites, the results of the refinement are Fe1: Fe; Fe2: Fe >> Mg; Mg3: Mg >> Fe. The H2O mols. that bond to the Al atom are extensively disordered, as has been obsd. in the isometric phases. The measured d. is 2.59(3) g/cm3 (by pycnometer), and the calcd. d. is 2.56(1) g/cm3.
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- Miami University, University of California, Santa Cruz, Mount Holyoke College
- Journal
- The Canadian Mineralogist
- Volume
- 46
- Pages
- 661-669
- No. of pages
- 9
- ISSN
- 0008-4476
- Publication date
- 2008
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105113 Crystallography, 105116 Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/c29f62e1-32d3-4c77-b87b-da946b72de2c