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: Fe_1.94(PO₃OH)₂(S_0.95O₄)(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) ų 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 (R₁ = 2.28% for 1138 F_o > 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.