• journal_title：Mineralogical Magazine
• Contributor：S. V. Krivovichev ; V. N. Yakovenchuk ; E. S. Zhitova ; A. A. Zolotarev ; Y. A. Pakhomovsky ; G. Yu. Ivanyuk
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2010-
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2010.074.5.833
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：74
• issue：5
• firstpage：833
• section：Articles

Quintinite-1M, [Mg₄Al₂(OH)₁₂](CO₃)(H₂O)₃, is the first monoclinic representative of both synthetic and natural layered double hydroxides (LDHs) based on octahedrally coordinated di- and trivalent metal cations. It occurs in hydrothermal veins in the Kovdor alkaline massif, Kola peninsula, Russia. The structure was solved by direct methods and refined to R₁ = 0.031 on the basis of 304 unique reflections. It is monoclinic, space group C2/m, a = 5.266(2), b = 9.114(2), c = 7.766(3) Å, β = 103.17(3)°, V = 362.9(2) ų. The diffraction pattern of quintinite-1M contains sharp reflections corresponding to the layer stacking sequence characteristic of the 3R rhombohedral polytype, and rows of weak superlattice reflections superimposed upon a background of streaks of modulated diffuse intensity parallel to c^*. These superlattice reflections indicate the formation of a 2-D superstructure due to Mg-Al ordering. The structure consists of ordered metal hydroxide layers and a disordered interlayer. As the unit cell contains exactly one layer, the polytype nomenclature dictates that the mineral be called quintinite-1M. The complete layer stacking sequence can be described as...=Ac₁B=Ba₁C=Cb₁A=... Quintinite-1M is isostructural with the monoclinic polytype of [Li₂Al₄(OH)₁₂](CO₃)(H₂O)₃.