| Reference Type | Journal (article/letter/editorial) |
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| Title | Gajardoite, KCa0.5As3+4O6Cl2·5H2O, a new mineral related to lucabindiite and torrecillasite from the Torrecillas mine, Iquique Province, Chile |
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| Journal | Mineralogical Magazine |
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| Authors | Kampf, Anthony R. | Author |
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| Nash, Barbara P. | Author |
| Dini, Maurizio | Author |
| Donoso, Arturo Molina A. | Author |
| Year | 2016 (December 1) | Volume | 80 |
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| Page(s) | 1265-1272 | Issue | 7 |
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| Publisher | Mineralogical Society |
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| Download URL | https://rruff.info/rruff_1.0/uploads/MM80_1265.pdf+ |
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| DOI | doi:10.1180/minmag.2016.080.065Search in ResearchGate |
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| Classification | Not set | LoC | Not set |
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| Mindat Ref. ID | 244845 | Long-form Identifier | mindat:1:5:244845:3 |
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| GUID | ab76d9a7-ea4a-4191-8525-58adde76b174 |
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| Full Reference | Kampf, Anthony R., Nash, Barbara P., Dini, Maurizio, Donoso, Arturo Molina A. (2016) Gajardoite, KCa0.5As3+4O6Cl2·5H2O, a new mineral related to lucabindiite and torrecillasite from the Torrecillas mine, Iquique Province, Chile. Mineralogical Magazine, 80 (7) 1265-1272 doi:10.1180/minmag.2016.080.065 |
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| Plain Text | Kampf, Anthony R., Nash, Barbara P., Dini, Maurizio, Donoso, Arturo Molina A. (2016) Gajardoite, KCa0.5As3+4O6Cl2·5H2O, a new mineral related to lucabindiite and torrecillasite from the Torrecillas mine, Iquique Province, Chile. Mineralogical Magazine, 80 (7) 1265-1272 doi:10.1180/minmag.2016.080.065 |
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| Abstract/Notes | The new mineral gajardoite (IMA2015-040), KCa0.5As3+4O6Cl2·5H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it occurs as a secondary alteration phase in association with native arsenic, arsenolite,chongite, talmessite and torrecillasite. Gajardoite occurs as hexagonal plates up to ∼100 μm in diameter and 5 μm thick, in rosette-like subparallel intergrowths. Crystals are transparent, with vitreous lustre and white streak. The Mohs hardness is ∼1½, tenacity is brittleand fracture is irregular. Cleavage is perfect on {001}. The measured density is 2.64 g/cm3 and the calculated density is 2.676 g/cm3. Optically, gajardoite is uniaxial (–) with ω = 1.780(3) and ε = 1.570(5) (measured in white light). The mineral is very slowly soluble in H2O and slowly soluble in dilute HCl at room temperature. The empirical formula, determined from electron-microprobe analyses, is (K0.77Ca0.71Na0.05Mg0.05)∑1.58As4O11Cl1.96H9.62.Gajardoite is hexagonal, P6/mmm, a = 5.2558(8), c = 15.9666(18) Å, V = 381.96(13) Å3 and Z = 1. The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 16.00(100)(001), 5.31(48)(003),3.466 (31)(103), 3.013(44)(104), 2.624(51)(006,110,111), 2.353(36)(113), 1.8647(21)(116,205) and 1.4605(17) (119,303,216). The structure, refined to R1 = 3.49% for 169 Fo > 4σF reflections, contains two types of layers. One layer of formulaKAs3+4O6Cl2 consists of two neutral As2O3 sheets, between which are K+ cations and on the outside of which are Cl– anions. This layer is topologically identical to a slice of the lucabindiite structureand similar to a slice of the torrecillasite structure. The second layer consists of an edge-sharing sheet of Ca(H2O)6 trigonal pyramids with isolated H2O groups centred in the hexagonal cavities in the sheet. |
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