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Carlfrancisite: Mn3 2+(Mn2+,Mg,Fe3+,Al)42(As3+O3)2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42, a new arseno-silicate mineral from the Kombat mine, Otavi Valley, Namibia

  • Frank C. Hawthorne EMAIL logo , Yassir A. Abdu , Neil A. Ball and William W. Pinch
Published/Copyright: March 7, 2015
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American Mineralogist
From the journal American Mineralogist Volume 98 Issue 10

Abstract

Carlfrancisite, Mn32+(Mn2+,Mg,Fe3+,Al)42(As3+O3)2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42, is a new mineral from the Kombat mine, Otavi Valley, Namibia, and occurs as curved platy aggregates ~2 cm across on a matrix of Mn arsenates and oxides. It is yellowy orange to pale yellow with a very pale-yellow streak, translucent with a vitreous to opalescent luster, and does not fluoresce under ultraviolet light. Cleavage is micaceous on {001}, and no parting or twinning was observed. Mohs hardness is 3, and carlfrancisite is brittle with a hackly fracture. The calculated density is 3.620 g/ cm3. Optical properties were measured with a Bloss spindle stage for the wavelength 590 nm using a gel filter. The indices of refraction are e = 1.756, w = 1.758, and it is non-pleochroic. Carlfrancisite is trigonal, space group R3̄c, a = 8.2238(2), c = 205.113(6) Å, V = 12 013.5(4) Å3, Z = 6, c:a = 1:24.941. The seven strongest lines in the X-ray powder-diffraction pattern are as follows: d (Å), I, (hkl): 2.826, 100, (2̄ 2 44); 2.371, 88, (2̄ 3 40, 1̄ 3 41); 1.552, 84, (1̄ 5 0); 2.676, 63, (2̄ 3 7); 3.243, 54, (0 1 56, 1̄ 2 39); 4.107, 48, (1̄ 2 0); 2.918, 47, (0 2 40). Chemical analysis by electron microprobe and crystalstructure refinement gave As2O5 13.07, As2O3 3.18, P2O5 0.50, V2O5 0.74, SiO2 8.96, Al2O3 0.78, FeO 0.22, MnO 53.25, MgO 9.37, H2O(calc) 8.42, sum 98.49 wt%. The H2O content and the valence states of As were determined by crystal-structure analysis. The empirical formula is Mn2+ 33.55Mg10.39Fe2+0.14Al0.68 As3+1.44(Si6.67P0.32V5+ 0.37As5+5.08)O54 (OH)42 on the basis of 96 anions with (OH) = 42 apfu. The structure of carlfrancisite is closely related to that of mcgovernite and turtmannite.

Keywords : Carlfrancisite; new mineral species; arseno-silicate; Tsumeb mine; Otavi Valley; Namibia; electron microprobe analysis; optical properties; chemical analysis; mcgovernite; turtmannite
Received: 2012-12-2
Accepted: 2013-5-17
Published Online: 2015-3-7
Published in Print: 2013-10-1

© 2015 by Walter de Gruyter Berlin/Boston

Articles in the same Issue

  1. Review article. The crystal structure and vibrational spectroscopy of jarosite and alunite minerals
  2. Versatile monazite: Resolving geological records and solving challenges in materials science. Petrogenesis of the Kulyk Lake monazite-apatite-Fe(Ti)-oxide occurrence revealed using in-situ LA-(MC)-ICP-MS trace element mapping, U-Pb dating, and Sm-Nd isotope systematics on monazite
  3. Amorphous Materials: Properties, structure, and durability. Analysis of H2O in silicate glass using attenuated total reflectance (ATR) micro-FTIR spectroscopy
  4. Unlocking the secrets of Al-tobermorite in Roman seawater concrete
  5. The determination of hydrogen positions in superhydrous phase B
  6. Carlfrancisite: Mn3 2+(Mn2+,Mg,Fe3+,Al)42(As3+O3)2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42, a new arseno-silicate mineral from the Kombat mine, Otavi Valley, Namibia
  7. Petrology and geochemistry of lunar granite 12032,366-19 and implications for lunar granite petrogenesis
  8. Extreme fractionation from zircon to hafnon in the Koktokay No. 1 granitic pegmatite, Altai, northwestern China
  9. Controls of P-T path and element mobility on the formation of corundum pseudomorphs in Paleoproterozoic high-pressure anorthosite from Sittampundi, Tamil Nadu, India
  10. Aluminum speeds up the hydrothermal alteration of olivine
  11. Iron pairs in beryl: New insights from electron paramagnetic resonance, synchrotron X-ray absorption spectroscopy, and ab initio calculations
  12. Effects of fluid and melt density and structure on high-pressure and high-temperature experimental studies of hydrogen isotope partitioning between coexisting melt and aqueous fluid
  13. DFT simulation of the occurrences and correlation of gold and arsenic in pyrite
  14. Crystal structure and hydration/dehydration behavior of Na2Mg(SO4)2·16H2O: A new hydrate phase observed under Mars-relevant conditions
  15. The diffusion behavior of hydrogen in plagioclase feldspar at 800–1000 °C: Implications for re-equilibration of hydroxyl in volcanic phenocrysts
  16. Quantification of dissolved CO2 in silicate glasses using micro-Raman spectroscopy
  17. Spin transition of Fe2+ in ringwoodite (Mg,Fe)SiO4 at high pressures
  18. P-V-T relations of γ-Ca3(PO4)2 tuite determined by in situ X-ray diffraction in a large-volume high-pressure apparatus
  19. Bonding and electronic changes in rhodochrosite at high pressure
  20. Growth of calcium carbonate in the presence of Se(VI) in silica hydrogel
  21. Thermodynamic properties of saponite, nontronite, and vermiculite derived from calorimetric measurements
  22. Far-infrared spectra of synthetic dioctahedral muscovite and muscovite–tobelite series micas: Characterization and assignment of the interlayer I–Oinner and I–Oouter stretching bands
  23. Phosphorus partitioning between olivine and melt: An experimental study in the system Mg2SiO4-Ca2Al2Si2O9-NaAlSi3O8-Mg3(PO4)2
  24. Olivine from spinel peridotite xenoliths: Hydroxyl incorporation and mineral composition
  25. Determination of the melting temperature of kaolinite by means of the Z-method
  26. Darrellhenryite, Na(LiAl2)Al6(BO3)3Si6O18(OH)3O, a new mineral from the tourmaline supergroup
  27. Nizamoffite, Mn2+Zn2(PO4)2(H2O)4, the Mn analogue of hopeite from the Palermo No. 1 pegmatite, North Groton, New Hampshire
  28. Mcalpineite from the Gambatesa mine, Italy, and redefinition of the species
  29. Rossiantonite, Al3(PO4)(SO4)2(OH)2(H2O)10·4H2O, a new hydrated aluminum phosphatesulfate mineral from Chimanta massif, Venezuela: Description and crystal structure
  30. Book Review
  31. Book Review
  32. Erratum
https://doi.org/10.2138/am.2013.4426
Keywords for this article
Carlfrancisite; new mineral species; arseno-silicate; Tsumeb mine; Otavi Valley; Namibia; electron microprobe analysis; optical properties; chemical analysis; mcgovernite; turtmannite

Articles in the same Issue

  1. Review article. The crystal structure and vibrational spectroscopy of jarosite and alunite minerals
  2. Versatile monazite: Resolving geological records and solving challenges in materials science. Petrogenesis of the Kulyk Lake monazite-apatite-Fe(Ti)-oxide occurrence revealed using in-situ LA-(MC)-ICP-MS trace element mapping, U-Pb dating, and Sm-Nd isotope systematics on monazite
  3. Amorphous Materials: Properties, structure, and durability. Analysis of H2O in silicate glass using attenuated total reflectance (ATR) micro-FTIR spectroscopy
  4. Unlocking the secrets of Al-tobermorite in Roman seawater concrete
  5. The determination of hydrogen positions in superhydrous phase B
  6. Carlfrancisite: Mn3 2+(Mn2+,Mg,Fe3+,Al)42(As3+O3)2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42, a new arseno-silicate mineral from the Kombat mine, Otavi Valley, Namibia
  7. Petrology and geochemistry of lunar granite 12032,366-19 and implications for lunar granite petrogenesis
  8. Extreme fractionation from zircon to hafnon in the Koktokay No. 1 granitic pegmatite, Altai, northwestern China
  9. Controls of P-T path and element mobility on the formation of corundum pseudomorphs in Paleoproterozoic high-pressure anorthosite from Sittampundi, Tamil Nadu, India
  10. Aluminum speeds up the hydrothermal alteration of olivine
  11. Iron pairs in beryl: New insights from electron paramagnetic resonance, synchrotron X-ray absorption spectroscopy, and ab initio calculations
  12. Effects of fluid and melt density and structure on high-pressure and high-temperature experimental studies of hydrogen isotope partitioning between coexisting melt and aqueous fluid
  13. DFT simulation of the occurrences and correlation of gold and arsenic in pyrite
  14. Crystal structure and hydration/dehydration behavior of Na2Mg(SO4)2·16H2O: A new hydrate phase observed under Mars-relevant conditions
  15. The diffusion behavior of hydrogen in plagioclase feldspar at 800–1000 °C: Implications for re-equilibration of hydroxyl in volcanic phenocrysts
  16. Quantification of dissolved CO2 in silicate glasses using micro-Raman spectroscopy
  17. Spin transition of Fe2+ in ringwoodite (Mg,Fe)SiO4 at high pressures
  18. P-V-T relations of γ-Ca3(PO4)2 tuite determined by in situ X-ray diffraction in a large-volume high-pressure apparatus
  19. Bonding and electronic changes in rhodochrosite at high pressure
  20. Growth of calcium carbonate in the presence of Se(VI) in silica hydrogel
  21. Thermodynamic properties of saponite, nontronite, and vermiculite derived from calorimetric measurements
  22. Far-infrared spectra of synthetic dioctahedral muscovite and muscovite–tobelite series micas: Characterization and assignment of the interlayer I–Oinner and I–Oouter stretching bands
  23. Phosphorus partitioning between olivine and melt: An experimental study in the system Mg2SiO4-Ca2Al2Si2O9-NaAlSi3O8-Mg3(PO4)2
  24. Olivine from spinel peridotite xenoliths: Hydroxyl incorporation and mineral composition
  25. Determination of the melting temperature of kaolinite by means of the Z-method
  26. Darrellhenryite, Na(LiAl2)Al6(BO3)3Si6O18(OH)3O, a new mineral from the tourmaline supergroup
  27. Nizamoffite, Mn2+Zn2(PO4)2(H2O)4, the Mn analogue of hopeite from the Palermo No. 1 pegmatite, North Groton, New Hampshire
  28. Mcalpineite from the Gambatesa mine, Italy, and redefinition of the species
  29. Rossiantonite, Al3(PO4)(SO4)2(OH)2(H2O)10·4H2O, a new hydrated aluminum phosphatesulfate mineral from Chimanta massif, Venezuela: Description and crystal structure
  30. Book Review
  31. Book Review
  32. Erratum
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