625 The Canadian Mineralogist Vol. 54, pp. 625-634 (2016) DOI: 10.3749/canmin.1500058 RAYGRANTITE, Pb10Zn(SO4)6(SiO4)2(OH)2, A NEW MINERAL ISOSTRUCTURAL WITH IRANITE, FROM THE BIG HORN MOUNTAINS, MARICOPA COUNTY, ARIZONA, USA § HEXIONG YANG ,MARCELO B. ANDRADE, ROBERT T. DOWNS, RONALD B. GIBBS, AND ROBERT A. JENKINS Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, U.S.A. ABSTRACT A new mineral species, raygrantite, ideally Pb10Zn(SO4)6(SiO4)2(OH)2, has been found in the Big Horn Mountains, Maricopa County, Arizona, USA. Associated minerals are galena, anglesite, cerussite, lanarkite, leadhillite, mattheddleite, alamosite, hydrocerussite, caledonite, and diaboleite. Raygrantite crystals are bladed with striations parallel to the elongated direction (the c axis). Twinning (fish-tail type) is pervasive on (1 2 1). The mineral is colorless, transparent with white streak, and has a vitreous luster. It is brittle and has a Mohs hardness of ~3; cleavage is good on {120} and no parting was observed. 3 The calculated density is 6.374 g/cm . Optically, raygrantite is biaxial (þ), with na ¼ 1.915(7), nb ¼ 1.981(7), nc ¼ 2.068(9), 2Vmeas ¼ 76(2)8, and 2Vcalc ¼ 858. It is insoluble in water, acetone, or hydrochloric acid. An electron microprobe analysis 2þ 2þ yielded the empirical formula Pb 9.81Zn 0.93(S1.00O4)6(Si1.05O4)2(OH)2. Raygrantite is a new member of the iranite mineral group. It is triclinic, with space group P1 and unit-cell parameters a 9.3175(4), b 11.1973(5), c 10.8318(5) A,˚ a 120.374(2), b 90.511(2), c 56.471(2)8, and V 753.13(6) A˚ 3. Its crystal structure, refined to R1 ¼ 0.031, is characterized by slabs that lie parallel to (120) of SO4 and SiO4 tetrahedra with ZnO4(OH)2 octahedra, held together by Pb2þ cations displaying a wide range of Pb–O bond distances. The discovery of raygrantite indicates that, in 2– 2– addition to complete OH–F and Cu–Zn substitutions, there is also a complete substitution between (CrO4) and (SO4) in the 2– iranite group of minerals, pointing to the possible existence of a number of other (SO4) -bearing iranite-type phases yet to be found or synthesized. Keywords: raygrantite, iranite, hemihedrite, crystal structure, X-ray diffraction, Raman spectra. INTRODUCTION ogical Association (IMA2013-001). Part of the co-type samples has been deposited in the University of A new mineral species, raygrantite, ideally Arizona Mineral Museum (Catalogue # 19345) and Pb10Zn(SO4)6(SiO4)2(OH)2, has been found in Arizo- the RRUFF Project (deposition # R120151, www:// na, USA. The mineral is named in honor of Dr. rruff.info/raygrantite). This paper describes the phys- Raymond W. Grant, a retired professor of geology at ical and chemical properties of raygrantite and its Mesa Community College in Mesa, Arizona. Dr. structural characterization based on single-crystal X- Grant’s primary scientific interest is minerals found in ray diffraction and Raman spectroscopic data. Arizona. His publications include several articles on Arizona mineral localities, the Checklist of Arizona SAMPLE DESCRIPTION AND EXPERIMENTAL METHODS rd Minerals, and the 3 edition of Mineralogy of Occurrence, physical and chemical properties, and Arizona. Ray Grant is the past and current President Raman spectra of the Mineralogical Society of Arizona, past Chair- man of the Flagg Mineral Foundation, and a principal Raygrantite was found at the Evening Star mine (a organizer of the Arizona Mineral Symposium. The former underground Cu-V-Pb-Au-Ag-W mine, also new mineral and its name have been approved by the previously called Old Queen Group or Silver Queen Commission on New Minerals and Nomenclature and mine), Big Horn District, Big Horn Mountains, Classification (CNMNC) of the International Mineral- Maricopa County, Arizona, USA (Lat. 338700 N, § Corresponding author e-mail address: [email protected] 626 THE CANADIAN MINERALOGIST FIG. 1. The rock sample on which the raygrantite crystals were found. Long. 1138210W). The crystals were found within a Raygrantite is insoluble in water, acetone, or hydro- small cavity in a mass of galena (Fig. 1). Associated chloric acid. minerals include galena, anglesite, cerussite, lanarkite, The chemical composition of raygrantite was leadhillite, mattheddleite, alamosite, hydrocerussite, determined with a CAMECA SX100 electron micro- caledonite, and diaboleite. Also, among the ‘‘rind’’ are probe operating at 20 kV and 20 nA with the beam fornacite, iranite, phoenicochroite, cerussite, and diameter of ~1 lm. The standards include wollastonite murdochite. Raygrantite is believed to have a second- for Si, barite for S, wulfenite for Pb, and ZnO for Zn, ary origin as a remnant of a galena-pyrite-chalcopyrite yielding an average composition (wt.%) (18 points) of vein. Mineral occurrences in the Big Horn district are SiO2 4.30(19), SO3 16.49(33), PbO 74.91(34), ZnO gold-rich, basement-hosted narrow quartz pods and 2.59(11), H2O 0.62 (added to bring the total close to veins associated with late Cretaceous intrusives (Allen the ideal value), and total ¼ 98.81(45). The presence of 1985). OH in raygrantite was also confirmed by Raman Raygrantite crystals are bladed and elongated along spectroscopic measurements and structure determina- the c axis (up to 0.05 3 0.10 3 0.30 mm), with tion (see below). Trace amounts of Cu, Cr, and F were striations parallel to the c axis (Fig. 2). Twinning (fish- observed from WDS, but they are under the detection tail type) is pervasive on (1 2 1), with the twin axis limits of electron microprobe analysis. The resultant along [0 1 0] (Fig. 3). The mineral is colorless in chemical formula, calculated on the basis of 34 O transmitted light, transparent with white streak, and atoms (from the structure determination), is has a vitreous luster. It is brittle and has a Mohs Pb9.81Zn0.93(S1.00O4)6(Si1.05O4)2(OH)2, which can be hardness of ~3; cleavage is good on {120} and no simplified as Pb10Zn(SO4)6(SiO4)2(OH)2. parting was observed. Fractures are uneven. The The Raman spectrum of raygrantite was collected calculated density is 6.37 g/cm3. Optically, raygrantite from a randomly oriented crystal with a Thermo is biaxial (þ), with na ¼ 1.915(7), nb ¼ 1.981(7), nc ¼ Almega microRaman system, using a 532-nm solid- 2.068(9), 2Vmeas ¼ 76(2)8, and 2Vcalc ¼ 858. Dispersion state laser with a thermoelectric cooled CCD detector. is strong (r . v) and absorption is Z . Y . X. The The laser is partially polarized with a 4 cm–1 resolution Gladstone Dale compatibility index is 0.04 (good). and a spot size of 1 lm. RAYGRANTITE, Pb10Zn(SO4)6(SiO4)2(OH)2, A NEW MINERAL 627 FIG. 2. A microscopic view of raygrantite crystals in a vug. X-ray crystallography index all the powder X-ray diffraction peaks. Thus, no Both the powder and single-crystal X-ray diffrac- unit-cell parameters were determined from the powder tion data for raygrantite were collected using a Bruker X-ray diffraction data. Listed in Table 1 are the X8 APEX2 CCD X-ray diffractometer equipped with measured powder X-ray diffraction data, along with graphite-monochromatized MoKa radiation. However, those calculated from the determined structure using due to severe overlaps, it is difficult to unambiguously the program XPOW (Downs et al. 1993). FIG. 3. A backscattered electron image of fish-tail type twinning in raygrantite. 628 THE CANADIAN MINERALOGIST TABLE 1. POWDER DIFFRACTION DATA FOR RAYGRANTITE Experimental Theoretical Intensity d-spacing (A˚ ) Intensity d-spacing (A˚ ) hkl 9 5.521 9.40 5.4655 1 1 1 56 4.753 60.42 4.7761 1 2 0 26 4.608 28.59 4.6153 1 22 32 4.288 28.48 4.2852 2 2 0 17 3.872 24.97 3.8800 2 0 1 18 3.604 (2 overlaps) 11.15 3.6297 1 32 18.91 3.5987 2 0 0 27 3.492 (3 overlaps) 11.11 3.4987 2 22 13.17 3.4878 0 13 16.76 3.4857 2 0 2 25 3.362 22.82 3.3614 1 23 63 3.267 100.00 3.2743 1 22 100 3.102 (3 overlaps) 76.06 3.1139 1 0 3 60.92 3.1055 3 2 0 15.81 3.0876 111 29 2.996 (3 overlaps) 12.99 3.0055 1 23 7.97 2.9841 2 12 9.88 2.9529 201 35 2.851 46.00 2.8590 0 2 1 31 2.783 45.34 2.7926 2 42 31 2.707 33.59 2.7185 2 23 20 2.648 17.20 2.6544 2 3 1 16 2.557 (2 overlaps) 6.40 2.5659 0 34 5.04 2.5425 3 0 2 15 2.535 (3 overlaps) 10.52 2.5396 3 22 7.03 2.5078 3 2 2 5.54 2.4875 0 3 0 7 2.379 (2 overlaps) 7.28 2.3991 3 0 0 3.71 2.3869 103 10 2.312 (3 overlaps) 8.23 2.3238 3 0 3 6.49 2.3142 4 3 0 6.93 2.3065 3 1 3 19 2.270 19.75 2.2826 0 42 15 2.155 (3 overlaps) 9.99 2.1649 0 0 4 10.68 2.1635 2 2 3 5.85 2.1565 3 3 2 21 2.128 (3 overlaps) 13.17 2.1371 4 42 7.77 2.1354 0 25 8.59 2.1163 301 10 2.062 17.43 2.0676 1 45 Single-crystal X-ray diffraction data were collected absorption using the Bruker program SADABS.