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Camaronesite, [Fe^(3+)(H_2O)_2(PO_3OH)]_2(SO_4)•1-2H_2O, a new phosphate-sulfate from the Camarones Valley, Chile, structurally related to taranakite

Kampf, A. R. and Mills, S. J. and Nash, B. P. and Housley, R. M. and Rossman, G. R. and Dini, M. (2013) Camaronesite, [Fe^(3+)(H_2O)_2(PO_3OH)]_2(SO_4)•1-2H_2O, a new phosphate-sulfate from the Camarones Valley, Chile, structurally related to taranakite. Mineralogical Magazine, 77 (4). pp. 453-465. ISSN 0026-461X. doi:10.1180/minmag.2013.077.4.05.

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Camaronesite (IMA 2012-094), [Fe^(3+)(H_2O)_2(PO_3OH)]_2(SO_4)•1-2H_2O, is a new mineral from near the village of Cuya in the Camarones Valley, Arica Province, Chile. The mineral is a low-temperature, secondary mineral occurring in a sulfate assemblage with anhydrite, botryogen, chalcanthite, copiapite, halotrichite, hexahydrite, hydroniumjarosite, pyrite, römerite, rozenite and szomolnokite. Lavender-coloured crystals up to several mm across form dense intergrowths. More rarely crystals occur as drusy aggregates of tablets up to 0.5 mm in diameter and 0.02 mm thick. Tablets are flattened on {001} and exhibit the forms {001}, {104}, {015} and {018}. The mineral is transparent with white streak and vitreous lustre. The Mohs hardness is 2½, the tenacity is brittle and the fracture is irregular, conchoidal and stepped. Camaronesite has one perfect cleavage on {001}. The measured and calculated densities are 2.43(1) and 2.383 g/cm^3, respectively. The mineral is optically uniaxial (+) with ω = 1.612(1) and ε = 1.621(1) (white light). The pleochroism is O (pale lavender) > E (colourless). Electron-microprobe analyses provided Fe_2O_331.84, P_2O_529.22, SO_315.74, H_2O 23.94 (based on O analyses), total 100.74 wt.%. The empirical formula (based on 2 P a.p.f.u.) is: Fe_(1.94)(PO_3OH)_2(S_(0.96)O_4)(H_2O)_4•1.46H_2O. The mineral is slowly soluble in concentrated HCl and extremely slowly soluble in concentrated H_2SO_4. Camaronesite is trigonal, R32, with cell parameters:a = 9.0833(5), c = 42.944(3) Å, V = 3068.5(3) Å3 and Z = 9. The eight strongest lines in the X-ray powder diffraction pattern are [d_(obs) Å (I)(hkl)]: 7.74(45)(101), 7.415(100)(012), 4.545(72)(110), 4.426(26)(018), 3.862(32)(021,202,116), 3.298(93)(027,119), 3.179(25)(208) and 2.818(25)(1•1•12,125). In the structure of camaronesite (R_1 = 2.28% for 1138 F_o > 4σF), three types of Fe octahedra are linked by corner sharing with (PO_3OH) tetrahedra to form polyhedral layers perpendicular to c with composition [Fe^(3+)(H_2O)_2(PO_3OH)]. Two such layers are joined through SO_4 tetrahedra (in two half-occupied orientations) to form thick slabs of composition [Fe^(3+)(H_2O)_2(PO_3OH)]_2(SO_4). Between the slabs are partially occupied H_2O groups. The only linkages between the slabs are hydrogen bonds. The most distinctive component in the structure consists of two Fe octahedra linked to one another by three PO_4 tetrahedra yielding an [Fe_2(PO_4)_3] unit. This unit is also the key component in the sodium super-ionic conductor (NASICON) structure and has been referred to as the lantern unit. The polyhedral layers in the structure of camaronesite are similar to those in the structure of taranakite. The Raman spectrum exhibits peaks consistent with sulfate, phosphate, water and OH groups.

Item Type:Article
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Kampf, A. R.0000-0001-8084-2563
Rossman, G. R.0000-0002-4571-6884
Additional Information:© 2013 The Mineralogical Society. Received 25 April 2013; Accepted 25 April 2013; AE: G.D. Gatta. Reviewer Giovanni Ferraris and Structures Editor, Peter Leverett, are thanked for their constructive comments on the manuscript. Arturo Molina is thanked for providing specimens of camaronesite. Work at the California Institute of Technology was supported by NSF grant EAR-0947956 and a grant from the Northern California Mineralogical Association. The remainder of this study was funded by the John Jago Trelawney Endowment to the Mineral Sciences Department of the Natural History Museum of Los Angeles County.
Funding AgencyGrant Number
Northern California Mineralogical AssociationUNSPECIFIED
Natural History Museum of Los Angeles County John Jago Trelawney EndowmentUNSPECIFIED
Subject Keywords:camaronesite; new mineral; sulfate; phosphate; Raman spectroscopy; crystal structure; taranakite; NASCION; Camarones Valley; Chile
Issue or Number:4
Record Number:CaltechAUTHORS:20130828-152157936
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:40982
Deposited By: Tony Diaz
Deposited On:30 Aug 2013 18:32
Last Modified:10 Nov 2021 04:24

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