Andrianovite, Na_(12)(K,Sr,Ce)_3Ca_6Mn_3Zr_3Nb(Si_(25)O_(73))(O, H_2O,OH)_5, a new potassium-rich mineral species of the eudialyte group from the Khibiny alkaline Pluton, Kola Peninsula, Russia

摘要

This paper presents the description of a new eudialyte-group mineral,which was named andriano-vite in honor of Valerii Ivanovich Andrianov(1938-1991),a famous Russian mathematician and crystallogra-pher,who developed the AREN software package for structural study of minerals with variable composition.The new mineral has been found in pegmatite from the Koashva open pit,Khibiny Pluton,Kola Peninsula,as rims 0.1-1.0 mm wide surrounding the crystals of typical eudialyte.Aegirine,sodalite,microcline,natrolite,lomonosovite,lamprophyllite,mosandrite,and villiaumite are associated minerals.Andrianovite is light yellow,with vitreous luster and stepped fracture.It is transparent or turbid,with a white streak.The new mineral is brittle;the Mohs hardness is 5.The cleavage is imperfect parallel to(001).The measured density is 2.93(2)g/cm~3(volumetric method);the calculated density is 3.02 g/cm~3.Andrianovite is optically uniaxial,negative;omega = 1.622(2),epsilon = 1.617(2).It is nonfluorescent and nonpleochroic.The new mineral slowly breaks down and gelates in 50% HCl and HNO3 at room temperature.It is trigonal,space group R3m.The unit cell dimensions are a =14.281(4),c = 30.243(7)A,V = 5342(4)A~3.The strongest reflections in the X-ray powder pattern [d,A(I,%)(hkl))are as follows:2.982(100)(315),2.860(94)(404),4.322(71)(205),3.222(70)(208),6.447(60)(104),3.170(50)(217),5.719(40)(202),3.540(38)(027).The chemical composition(electron microprobe,H2O and CO2 determined by chemical analysis)is as follows,wt %:11.61 Na2O,2.05 K2O,10.26 CaO,3.11 SrO,0.19 BaO,3.97 MnO,2.43 FeO,0.81 La2O3,1.73 Ce2O3,0.52 Nd2O3,0.28 Y2O3,0.02 Al2O3,47.06 SiO2,0.12 TiO2,11.32 ZrO2,0.26 HfO2,2.84 Nb2O5,0.31 Cl,0.57 CO2,0.87 H2O,-O = 0.07 Cl2;total is 100.26.The empirical formula at SIGMA cat = 53(Z = 3)is Na_(12.09)(K_(1.40)Sr_(0.97)REE_(0.60)Ba_(0.04))_(SIGMA 3.01)(Ca_(5.90)Y_(0.08))_(SIGMA 5.98)(Mn_(1.81)Fe_(1.19)~(2+))_(SIGMA 2.90)(Zr_(2.96)Hf_(0.04))_(SIGMA 3.0)(Nb_(0.69)Si_(0.27)Ti_(0.05)Al_(0.01))_(SIGMA 1.02)(Si_(25)O_(73))[(O_(2.14)(OH)_(0.52)][(H2O)_(1.30)(CO3)_(0.42)Cl_(0.28)]_(SIGMA 2.0).The simplified formula is Na_(12)(K,Sr,Ce)3Ca6(Mn,Fe)3Zr3Nb(Si_(25)O_(73))(O,H2O,OH)5.The infrared spectrum is given,and the crystal structure is described.The position of andrianovite in the crystallochemical taxonomy of the eudialyte group is shown,and its relationships with other eudialyte-group minerals(kentbrooksite,carbokentbrooksite,georgbar-sanovite,etc.)are characterized.The type material of andrianovite has been deposited in the Fersman Mineral-ogical Museum,Russian Academy of Sciences,Moscow.