• journal_title：The Canadian Mineralogist
• Contributor：Andreas Ertl ; M. Darby Dyar ; John M. Hughes ; Franz Brandstätter ; Mickey E. Gunter ; Markus Prem ; Ronald C. Peterson
• Publisher：Mineralogical Association of Canada
• Date：2008-
• Format：text/html
• Language：en
• Identifier：10.3749/canmin.46.3.661
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：46
• issue：3
• firstpage：661
• section：Articles

Pertlikite, a new member of the voltaite group, is the tetragonal Mg-dominant analogue of the isometric phases voltaite and zincovoltaite. At its type locality, Madeni Zakh, Iran, the mineral occurs in a pyrite-bearing trachytic eruptive rock, and probably formed after the decomposition of pyrite. Pertlikite forms single crystals up to 1 cm; the phase is associated with metavoltine, botryogen, pyrite and alunite. In contrast to voltaite and zincovoltaite, the optical properties and the single-crystal study of the structure (R1 = 0.022) confirm the tetragonal symmetry, ω = 1.590(2), ε = 1.586(2), space group I4₁/acd, a 19.2080(3), c 27.2158(7) Å, V 10041.2(6) ų, and Z = 8. The results of the chemical analysis, in combination with the Mössbauer data and the crystal-structure refinement, give the formula (K_1.98Na_0.01)_∑1.99^M2(Fe²⁺_1.13Mg_0.49Mn²⁺_0.27Fe³⁺_0.10Zn_0.01)_∑2.00^M3(Mg_2.52Fe³⁺_1.49)_∑4.01^M1Fe³⁺_2.00 Al_1.00 (SO₄)_12.00·18 H₂O, which can be simplified to an ideal formula: K₂^M2(Fe²⁺,Mg)₂^M3(Mg,Fe³⁺)₄^M1Fe³⁺₂ Al (SO₄)₁₂·18 H₂O. The strongest eight lines of the powder pattern [d in Å(I)(hkl)] are: 5.543(28)(132), 3.396(100)(440), 3.136(21) (345), 3.038(39)(444), 2.848(31)(361), 2.534(21)(273), 2.078(29)(567) and 1.601(21)(6104). The unit-cell parameters refined from the powder data (CuKα radiation) are a 19.2167(2), c 27.1976(4) Å. The tetragonal structure of pertlikite results from Mg,Fe order at the Fe2 site. Relative to the isometric voltaite and zincovoltaite, the Fe2 site splits to create a site that is predominantly Mg (Mg3) and another that is dominantly Fe (Fe2) in pertlikite. For the three metal sites, the results of the refinement are Fe1: . Fe; Fe2: Fe >> Mg; Mg3: Mg >> Fe. The H₂O molecules that bond to the Al atom are extensively disordered, as has been observed in the isometric phases. The measured density is 2.59(3) g/cm³ (by pycnometer), and the calculated density is 2.56(1) g/cm³. The name honors Franz Pertlik, Professor of Mineralogy and Crystallography, University of Vienna, Austria, in recognition of his extensive work on the crystal chemistry of minerals.