TY - JOUR

T1 - Akopovaite, Li2Al4(OH)12(CO3)(H2O)3, a new Li member of the hydrotalcite supergroup from Turkestan Range, Kyrgyzstan

AU - Karpenko, Vladimir Yu

AU - Zhitova, Elena S.

AU - Pautov, Leonid A.

AU - Agakhanov, Atali A.

AU - Siidra, Oleg I.

AU - Krzhizhanovskaya, Maria G.

AU - Rassulov, Victor A.

AU - Bocharov, Vladimir N.

PY - 2020/4/1

Y1 - 2020/4/1

N2 - Akopovaite, ideally Li2Al4(OH)12(CO3)(H2O)3, is a new hydrotalcite-supergroup mineral from the Karasu-Karavshinskoye Sn deposit, Turkestan Range, Kyrgyzstan. It occurs as white or pale yellowish rosette-like aggregates that are composed of tiny curved plates up to 20-30 μm. Akopovaite is associated with gibbsite, quartz, albite, microcline, muscovite, montebrasite, siderite, schorl and birnessite-like Fe-Mn oxides. Akopovaite has a perfect cleavage along {001}, the mineral is transparent and very soft (VHN = 24 that corresponds to Mohs hardness of ca. 1). Dmeas = 2.12(2) g/cm3 and Dcalc = 2.106 g/cm3. The Raman spectra contain bands of carbonate groups and bands of O-H stretching vibrations. The chemical composition (wt.%, electron microprobe for Al and Fe; ICP-OES for Li; CHN method for CO2 and H2O) is Li2O 6.43, Al2O3 45.79, Fe2O3 0.27, CO2 10.09, H2O 36.1, total 98.68. The empirical formula based on (Li + Al + Fe) = 6 apfu is Li1.94(Al4.05Fe0.02)Σ4.07(OH)12(CO3)1.03(H2O)3.03. The crystal structure was refined by the Rietveld method with RB = 0.006 and Rwp = 0.014. Akopovaite is monoclinic, C2/m, a = 5.0953(6), b = 8.877(1), c = 7.806(1) Å, β = 102.572(6)°, V = 344.61(8) Å3 and Z = 1. The polytype should be denoted as 1M. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 7.66(100)(001), 4.397(27)(020), 3.821(45)(002,021), 2.4881(27)(200), 2.2273(16)(201) and 1.9027(18)(202). Akopovaite is the first naturally occurring hydrotalcite-supergroup carbonate species of Al and Li; its synthetic analogue is known.

AB - Akopovaite, ideally Li2Al4(OH)12(CO3)(H2O)3, is a new hydrotalcite-supergroup mineral from the Karasu-Karavshinskoye Sn deposit, Turkestan Range, Kyrgyzstan. It occurs as white or pale yellowish rosette-like aggregates that are composed of tiny curved plates up to 20-30 μm. Akopovaite is associated with gibbsite, quartz, albite, microcline, muscovite, montebrasite, siderite, schorl and birnessite-like Fe-Mn oxides. Akopovaite has a perfect cleavage along {001}, the mineral is transparent and very soft (VHN = 24 that corresponds to Mohs hardness of ca. 1). Dmeas = 2.12(2) g/cm3 and Dcalc = 2.106 g/cm3. The Raman spectra contain bands of carbonate groups and bands of O-H stretching vibrations. The chemical composition (wt.%, electron microprobe for Al and Fe; ICP-OES for Li; CHN method for CO2 and H2O) is Li2O 6.43, Al2O3 45.79, Fe2O3 0.27, CO2 10.09, H2O 36.1, total 98.68. The empirical formula based on (Li + Al + Fe) = 6 apfu is Li1.94(Al4.05Fe0.02)Σ4.07(OH)12(CO3)1.03(H2O)3.03. The crystal structure was refined by the Rietveld method with RB = 0.006 and Rwp = 0.014. Akopovaite is monoclinic, C2/m, a = 5.0953(6), b = 8.877(1), c = 7.806(1) Å, β = 102.572(6)°, V = 344.61(8) Å3 and Z = 1. The polytype should be denoted as 1M. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 7.66(100)(001), 4.397(27)(020), 3.821(45)(002,021), 2.4881(27)(200), 2.2273(16)(201) and 1.9027(18)(202). Akopovaite is the first naturally occurring hydrotalcite-supergroup carbonate species of Al and Li; its synthetic analogue is known.

KW - akopovaite

KW - carbonate

KW - dritsite

KW - hydrotalcite supergroup

KW - Karasu-Karavshinskoye Sn deposit

KW - layered double hydroxides

KW - new mineral

KW - polytype

KW - quintinite

KW - Turkestan Range

UR - http://www.scopus.com/inward/record.url?scp=85084605835&partnerID=8YFLogxK

U2 - 10.1180/mgm.2020.10

DO - 10.1180/mgm.2020.10

M3 - Article

AN - SCOPUS:85084605835

VL - 84

SP - 301

EP - 311

JO - Mineralogical Magazine

JF - Mineralogical Magazine

SN - 0026-461X

IS - 2

ER -