Sergevanite, Na15(Ca3Mn3)(Na2Fe)Zr3Si26O72(OH)3·H2O, a new eudialyte-group mineral from the Lovozero alkaline massif, Kola Peninsula

Nikita V. Chukanov, Sergey M. Aksenov, Igor V. Pekov, Dmitriy I. Belakovskiy, Svetlana A. Vozchikova, Sergey N. Britvin

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The new eudialyte-group mineral sergevanite, ideally Na 15(Ca 3Mn 3)(Na 2Fe)Zr 3Si 26O 72(OH) 3·H 2O, was discovered in highly agpaitic foyaite from the Karnasurt Mountain, Lovozero alkaline massif, Kola Peninsula, Russia. The associated minerals are microcline, albite, nepheline, arfvedsonite, aegirine, lamprophyllite, fluorapatite, steenstrupine-(Ce), ilmenite, and sphalerite. Sergevanite forms yellow to orange-yellow anhedral grains up to 1.5 mm across and the outer zones of some grains of associated eudialyte. Its luster is vitreous, and the streak is white. No cleavage is observed. The Mohs’ hardness is 5. Density measured by equilibration in heavy liquids is 2.90(1) g/cm 3. Calculated density is equal to 2.906 g/cm 3. Sergevanite is nonpleochroic, optically uniaxial, positive, with x ¼ 1.604(2) and e ¼ 1.607(2) (k ¼ 589 nm). The infrared spectrum is given. The chemical composition of sergevanite is (wt.%; electron microprobe, H 2O determined by HCN analysis): Na 2O 13.69, K 2O 1.40, CaO 7.66, La 2O 3 0.90, Ce 2O 3 1.41, Pr 2O 3 0.33, Nd 2O 3 0.64, Sm 2O 3 0.14, MnO 4.15, FeO 1.34, TiO 2 1.19, ZrO 2 10.67, HfO 2 0.29, Nb 2O 5 1.63, SiO 2 49.61, SO 3 0.77, Cl 0.23, H 2O 4.22, –O¼Cl –0.05, total 100.22. The empirical formula (based on 25.5 Si atoms pfu, in accordance with structural data) is H 14.46Na 13.64K 0.92Ca 4.22Ce 0.27La 0.17Nd 0.12Pr 0.06Sm 0.02Mn 1.81 Fe 0.58Ti 0.46Zr 2.67Hf 0.04Nb 0.38Si 25.5S 0.30Cl 0.20O 81.35. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is trigonal, space group R3, with a ¼ 14.2179(1) Å, c ¼ 30.3492(3) Å, V ¼ 5313.11(7) Å 3, and Z ¼ 3. In the structure of sergevanite, Ca and Mn are ordered in the six-membered ring of octahedra (at the sites M1 1 and M1 2), and Na dominates over Fe at the M2 site. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 7.12 (70) (110), 5.711 (43) (202), 4.321 (72) (205), 3.806 (39) (033), 3.551 (39) (220, 027), 3.398 (39) (313), 2.978 (95) (345), 2.855 (100) (404). Sergevanite is named after the Sergevan’ River, which is near the discovery locality.

Original languageEnglish
Pages (from-to)421-436
Number of pages16
JournalCanadian Mineralogist
Issue number4
StatePublished - 1 Jul 2020

Scopus subject areas

  • Geochemistry and Petrology


  • Crystal structure
  • Eudialyte group
  • IR spectroscopy
  • Lovozero massif
  • New mineral
  • Peralkaline rocks
  • Sergevanite


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