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Kayupovaite, Na 2 Mn 10 [(Si 14 Al 2 )O 38 (OH) 8 ] ⋅ 7H 2 O – a new stilpnomelane-related mineral from the Ushkatyn-III deposit, Kazakhstan

Year: 2025

Type: article

Abstract: Kayupovaite, with the idealized formula Na 2 Mn 10 [(Si 14 Al 2 )O 38 (OH) 8 ]⋅7H 2 O, is a new mineral named in honor of Maria Mikhailovna Kayupova (1921–1980), the mineralogist of the Satpaev Institute of Geological Sciences (Alma-Ata, USSR) who studied the Ushkatyn-III complex baryte–lead/iron–manganese deposit, Karagandy Province, Kazakhstan, the type of locality of the described mineral. Kayupovaite forms coarse lamellar (typically bent and split), light-gray, greasy luster crystals up to 0.2×0.15×0.01 mm in size, combined into radial, scaly, or lamellar aggregates up to 3×3×0.5 cm and embedded in a calcite–rhodonite matrix. Optically, in transmitted light, kayupovaite is colorless, with undulatory extinction due to the crystal curvature. It is non-pleochroic and biaxial (–), with α of 1.551(4) and β = γ 1.586(2), 2Vmeas=3±1°. Kayupovaite is monoclinic and of space group C 2/ c , with a =24.9149(9), b =16.4343(5), c =22.3974(7) Å, β =94.408(3)°, V =9143.7(5) Å 3 , and Z =8. The strongest lines of the powder X-ray diffraction pattern ( d in Å ( I ) ( hkl )) are as follows: 12.34(100)(200), 3.45(8)(71−1), 3.09(8)(800), 2.85(100)(121), 2.5946(12)(714), 2.642(11)(354), 2.614(7)(40−8), and 2.414(7)(554). The Raman spectrum of kayupovaite contains the following bands (cm −1 ): 3635 and 3560 (O–H stretching vibrations of OH groups and H 2 O molecules); 1041, 768, 742, and 717 (Si–O and Al–O stretching modes); 657, 532, 499, 460, 405, 374, and 333 (Mn–O stretching and Si–O–Si modes); and 304, 291, 224, 157, and 100 (lattice modes). The absorption bands of the infrared spectrum are as follows (cm −1 ): 3629, 3511, and 3390 (O–H stretching vibrations of OH groups and H 2 O molecules); 1640 (H 2 O bending vibrations); 1020 (Si–O stretching vibrations); 778 ( IV Al–O stretching vibrations); 724 (Mn–O–H bending mode); 651 (O–Si–O bending mode); and 459 (Mn 2+ –O stretching vibrations). The empirical formula of kayupovaite, calculated on the basis of (O + OH) = 46 atoms per formula unit, is (Na 0.91 K 0.46 Ca 0.14 ) Σ1.51 (Mn9.292+Mg 0.89 Zn 0.02 ) Σ10.20 [(Si 14.28 Al 1.61 ) Σ15.89 O 38 (OH) 8 ]⋅7.23H 2 O. The mineral belongs to the group of modulated manganese phyllosilicates and is structurally related to stilpnomelane. The absence of iron in the mineral is a result of oxidative Mn–Fe fractionation during the formation of braunite-rich Mn ores.

Source: European Journal of Mineralogy

DOI: 10.5194/ejm-37-829-2025