Selsurtite, (H₃O)₁₂Na₃(Ca₃Mn₃)(Na₂Fe)Zr₃□Si[Si₂₄O₆₉(OH)₃](OH)Cl⋅H₂O, a new eudialyte-group mineral from the Lovozero alkaline massif, Kola Peninsula, Russia

Abstract

The new eudialyte-group mineral selsurtite, ideally (H 3 O) 12 Na 3 (Ca 3 Mn 3 )(Na 2 Fe)Zr 3 Si[Si 24 O 69 (OH) 3 ](OH)Cl•H 2 O, was discovered in metasomatic peralkaline rock from the Flora mountain, the northern spur of the Selsurt mountain, Lovozero alkaline massif, Kola Peninsula, Russia. The associated minerals are aegirine, albite and orthoclase, as well as accessory lorenzenite, calciomurmanite, natrolite, lamprophyllite, and sergevanite. Selsurtite occurs as brownish-red to reddish-orange, equant or flattened on (0001) crystals up to 2 mm across and elongate crystals up to 3 cm long. The main crystal forms are {0001}, {11-20}, and {10-11}. Selsurtite is brittle, with the Mohs' hardness of 5. No cleavage is observed. Parting is distinct on (001). D(meas) = 2.73(2), D(calc) = 2.722 g•cm -3 . Selsurtite is optically uniaxial, negative, with  = 1.598(2) and  = 1.595(2). The chemical composition is (wt.%, electron

Chlorine-Deficient Analog of Taseqite from Odikhincha Massif (Russia): Genesis and Relation with Other Sr-Rich Eudialyte-Group Minerals

“…In the Illimaussak, Pilansberg and Khibiny massifs, taseqite and taseqite-like eudialyte is formed during the hydrothermal stage [35][36][37] and is accompanied by a mineral association largely similar to the mineral association of the studied pegmatite. Thus, despite being in the complex of alkaline-ultrabasic rocks, the pegmatite of the Odikhincha massif is mineralogically similar to the pegmatites of the agpaite-syenite alkaline massifs [12].…”

“…The spatial association of pegmatite with carbonatite requires a comparison with the "agpaitic crossed pegmatites" of the Kovdor massif. However, in the "crossing pegmatites"of the Kovdorsky massif (as well as the Inagli agpaitic pegmatites, less studied but similar to the Kovdorsky ones) the influence of the carbonate environment is expressed in the presence of high-calcium representatives of the eudialyte group, including those containing CO [12,44]. In the contrast, the Odikhincha pegmatite contains a highstrontium rare-metal mineralization, including taseqite-like mineral of the eudialyte group, as well as rinkite, mosandrite, lamprophyllite and Sr-rich apatite mineral.…”

“…EGMs play a role of accessory and even rock-forming components in peralkaline silica-saturated [8] and silica-undersaturated agpaitic rocks. EGMs are generally found in massifs of agpaitic nepheline syenites, such as Khibiny, Lovozero, Ilimaussaq [9], etc., and much rarely, EGM-bearing rocks may be found in alkaline-ultramafic massifs, such as Konder [10] and Inagli [11], and extremely rarely, in typical alkaline-ultramafic massifs with carbonatites, such as Kovdor [12] or Salpeterkop [13]. In this paper, we report the mineralogical features of EGM found in the pegmatite of the Odikhincha massif, a typical alkaline-ultramafic-carbonatite massif.…”

Synthesis of Fe-deficient eudialyte analogues: Relationships between the composition of the reaction system and crystal-chemical features of the products

“…The product with the highest Ca content (Route 2b) is associated with golyshevite (Na,Ca) 10 Ca 9 Fe 2 Zr 3 NbSi 25 O 72 (OH) 3 (CO 3 )⋅H 2 O (Chukanov et al, 2005), from which it differs in the absence of Nb and a low Fe content. By analogy with golyshevite, it can be assumed that in this compound, Ca in excess of 6 apfu is concentrated at the N4 site.…”

“…These minerals are typical for peralkaline rocks of ultrabasic-alkaline massifs with carbonatites. Carbonatites are considered as the source of calcium and CO 3 2groups (Rozenberg et al, 2005;Chukanov et al, 2005;Moiseev, Chukanov, 2006). In the structures of some Type-3 EGM, strontium can have the same role as calcium (Rastsvetaeva et al, 2018;Gritsenko et al, 2020).…”