Hostname: page-component-cd9895bd7-fscjk Total loading time: 0 Render date: 2024-12-24T02:18:16.980Z Has data issue: false hasContentIssue false
  • English
  • Français

Bobmeyerite, a new mineral from Tiger, Arizona, USA, structurally related to cerchiaraite and ashburtonite

Published online by Cambridge University Press:  05 July 2018

A. R. Kampf ,
J. J. Pluth ,
Y.-S. Chen ,
A. C. Roberts  and
R. M. Housley
A. R. Kampf*
Affiliation:
Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, USA
J. J. Pluth
Affiliation:
Department of Geophysical Sciences, Center for Advanced Radiation Sources, University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637-1434, USA
Y.-S. Chen
Affiliation:
Center for Advanced Radiation Sources, University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637-1434, USA
A. C. Roberts
Affiliation:
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada
R. M. Housley
Affiliation:
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
*
* E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

Bobmeyerite, Pb4(Al3Cu)(Si4 O12)(S0.5Si0.5O4)(OH)7 Cl(H2O)3, is a new mineral from the Mammoth - Saint Anthony mine, Tiger, Pinal County, Arizona, USA. It occurs in an oxidation zone assemblage attributed to progressive alteration and crystallization in a closed system. Other minerals in this assemblage include atacamite, caledonite, cerussite, connellite, diaboleite, fluorite, georgerobinsonite, hematite, leadhillite, matlockite, murdochite, phosgenite, pinalite, quartz, wulfenite and yedlinite. Bobmeyerite occurs as colourless to white or cream-coloured needles, up to 300 m m in length, that taper to sharp points. The streak is white and the lustre is adamantine, dull or silky. Bobmeyerite is not fluorescent. The hardness could not be determined, the tenacity is brittle and no cleavage was observed. The calculated density is 4.381 g cm-3. Bobmeyerite is biaxial (-) with α ≈ β = 1.759(2), γ = 1.756(2) (white light), it is not pleochroic; the orientation is X = c; Y or Z = a or b. Electron-microprobe analyses provided the empirical formula Pb3.80Ca0.04Al3.04Cu2+0.96Cr3+0.13Si4.40S0.58O24.43Cl1.05F0.52H11.83. Bobmeyerite is orthorhombic (pseudotetragonal), Pnnm with unit-cell parameters a = 13.969(9), b = 14.243(10), c = 5.893(4) Å, V = 1172.5(1.4) Å3 and Z = 2. The nine strongest lines in the X-ray powder diffraction pattern, listed as [dobs (Å)(I)(hkl)], are as follows: 10.051(35)(110); 5.474(54)(011,101); 5.011(35)(220); 4.333(43)(121,211); 3.545(34)(040,400); 3.278(77)(330,231,321); 2.9656(88)(141,002,411); 2.5485(93)(051,222,501); 1.873(39)(multiple). Bobmeyerite has the same structural framework as cerchiaraite and ashburtonite. In the structure, which refined to R1 = 0.079 for 1057 reflections with F > 4σF, SiO4 tetrahedra share corners to form four-membered Si4O12 rings centred on the c axis. The rings are linked by chains of edge-sharing AlO6 octahedra running parallel to [001]. The framework thereby created contains large channels, running parallel to [001]. The Cl site is centred on the c axis alternating along [001] with the Si4O12 rings. Two non-equivalent Pb atoms are positioned around the periphery of the channels. Both are elevencoordinate, bonding to the Cl atom on the c axis, to eight O atoms in the framework and to two O (H2O) sites in the channel. The Pb atoms are off-centre in these coordinations, as is typical of Pb2+ with stereo-active lone-electron pairs. A (S, Si, Cr)O4 group is presumed to be disordered in the channel. The name honours Robert (Bob) Owen Meyer, one of the discoverers of the new mineral.

Keywords

bobmeyeritecerchiaraiteashburtonitenew mineralcrystal structureIR spectroscopyelectron microprobe analysiscyclosilicatePb2+ 6s2 lone-electron pairMammoth–Saint Anthony mineTigerArizona
Type
Letter
Information
Mineralogical Magazine , Volume 77 , Issue 1 , February 2013 , pp. 81 - 91
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2013

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Basso, R., Lucchetti, G., Zefiro, L. and Palenzona, A. (2000) Cerchiaraite, a new natural Ba-Mn-mixedanion silicate chloride from the Cerchiara mine, northern Apennines, Italy. Neues Jahrbuch für Mineralogie, Monatshefte, 2000, 373–384.Google Scholar
Bideaux, R.A. (1980) Tiger, Arizona. Mineralogical Record, 11, 155–181.Google Scholar
Brown, I.D. and Altermatt, D. (1985) Bond-valence parameters from a systematic analysis of the inorganic crystal structure database. Acta Crystallographica, B41, 244–247.CrossRefGoogle Scholar
Bruker, (2005) SAINT-Plus and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.Google Scholar
Grice, J.D., Nickel, E.H. and Gault, R.A. (1991) Ashburtonite, a new bicarbonate-silicate mineral from Ashburton Downs, Western Australia: description and structure determination. American Mineralogist, 76, 1701–1707.Google Scholar
Kampf, A.R., Roberts, A.C., Venance, K.E., Carbone, C., Belmonte, D., Dunning, G.E. and Walstrom, R.E. (2013) Cerchiaraite-(Fe) and cerchiaraite-(Al), two new barium cyclosilicate chlorides from Italy and California (USA). Mineralogical Magazine, 77, 69–80.CrossRefGoogle Scholar
Mandarino, J.A. (1981) The Gladstone–Dale relationship: part IV. The compatibility concept and its application. The Canadian Mineralogist, 19, 441–450.Google Scholar
Sheldrick, G.M. (2008) SHELXL97 – Program for the Refinement of Crystal Structures. University of Göttigen, Göttigen, Germany.Google Scholar
Smith, D.G.W. and Nickel, E.H. (2007) A system for codification for unnamed minerals: report of the Subcommittee for Unnamed Minerals of the IMA Commission on New Minerals, Nomenclature and Classification. The Canadian Mineralogist, 45, 983–1055.CrossRefGoogle Scholar
Supplementary material: File

Kampf et al. supplementary material

Structure factors

Download Kampf et al. supplementary material(File)
File 69.6 KB