Camaronesite, [Fe3+(H2O)2(PO3OH)]2(SO4) ·1-2H2O,

a new phosphate-sulfate from the Camarones Valley, Chile,

structurally related to taranakite.

Kampf AR,
Mineral Sciences Department, Natural History Museum of Los Angeles County
900 Exposition Blvd., Los Angeles, CA 90007, USA

Stuart J. Mills
Geosciences, Museum Victoria, GPO Box 666, Melbourne 3001, Victoria, Australia

Barbara P. Nash
Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, USA

Housley RM, George R. Rossman
Division of Geological and Planetary Sciences, California Institute of Technology,
Pasadena, California 91125-2500, USA

Maurizio Dini
Pasaje San Agustin 4045, La Serena, Chile


Camaronesite (IMA 2012-094), [Fe3+(H2O)2(PO3OH)]2(SO4) ·1-2H2O, 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 an oxidized sulfate assemblage in association with actinolite, anhydrite, botryogen, copiapite, halotrichite, pyrite, römerite, rozenite and szomolnokite. Crystals, often heavily included by anhydrite, form lavender-coloured, dense intergrowths, with cleavage surfaces up to several mm across. More rarely crystals occur as pink to pale lavender tablets to 0.5 mm in diameter and 0.02 mm thick forming drusy aggregates lining vughs and seams. Tablets are flattened on {001} and exhibit the forms {001}, {104}, {015} and {018}. The mineral is transparent and has a white streak and vitreous luster. 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 2.387 g/cm3, 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). The electron-microprobe analyses (average of 10) provided: Fe2O3 31.8, P2O5 29.2, SO3 15.7, H2O 23.9 (structure), total 100.6 wt%. The empirical formula (based on 2 P apfu) is: Fe1.94(PO3OH)2(S0.95O4)(H2O)4·1.45H2O. The mineral is slowly soluble in cold, concentrated HCl and extremely slowly soluble in concentrated H2SO4. Camaronesite is trigonal, R32, with the 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 [dobs 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 (R1 = 2.28% for 1138 Fo > 4sF), three types of insular Fe octahedra are linked by corner sharing with PO3(OH) and SO4 tetrahedra to form thick layers perpendicular to c. The slabs are linked to one another only via hydrogen bonding. The most distinctive component in the structure consists of two Fe octahedra linked to one another by three PO4 tetrahedra yielding a [Fe2(PO4)3] unit. This unit is also the key component in the sodium super ion conductor (NASICON) structure and has been referred to as the lantern unit. The Raman spectrum exhibits peaks consistent with sulfate, phosphate, water and OH groups.