• journal_title：The Canadian Mineralogist
• Contributor：Dmitry Yu. Pushcharovsky ; Yulia S. Lebedeva ; Natalia V. Zubkova ; Marco Pasero ; Marco Bellezza ; Stefano Merlino ; Nikita V. Chukanov
• Publisher：Mineralogical Association of Canada
• Date：2004-
• Format：text/html
• Language：en
• Identifier：10.2113/gscanmin.42.3.723
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：42
• issue：3
• firstpage：723
• section：Articles

id="p-1">Sturmanite, ideally Ca₆Fe₂ ³⁺ (SO₄)_2.5[B(OH)₄](OH)₁₂·25H₂O, is trigonal, P31c, Z = 2, with a 11.188(9), c 21.91(7) Å, V 2375.1(5) ų. The crystal structure has been refined to an R index of 0.079. As in the case of ettringite, two coaxial elements parallel to [001] can be considered as the most distinctive features of sturmanite. The main one is a column of polyhedra formed by Fe-octahedra and Ca-polyhedra. The Fe(OH)₆ octahedra are located along the three-fold axes that pass through the origin of the cell. They are linked to three ^VIIICa-polyhedra, located around the three-fold axes, in between the Fe(OH)₆ octahedra. The second structural element parallel to [001] contains [SO₄] and B(OH)₄ tetrahedra; it is located along three-fold axes at (⅓, ⅔, z) and (⅔, ⅓, z). Both structural modules are linked to each other by a complex system of hydrogen bonds. On the basis of a complete determination of the structure, the chemical composition of sturmanite is close to Ca₆[Fe_0.6 ³⁺Al_0.2Mn_0.2 ⁴⁺]₂ [SO₄]_2.7[B(OH)₃]_0.3 [B(OH)₄](OH)₁₂·24H₂O.