Zvyaginite
Zvyaginite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₂ZnTiNb₂(Si₂O₇)₂O₂(OH)₂(H₂O)₄.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Seidozerite-Lamprophyllite structural group.
Key properties: Mohs hardness 2.5–3; specific gravity 2.88; White streak; Pearly on crystal faces, greasy on breaks luster; optically biaxial.
IMA symbol Zvy, IMA status: approved, named in 2013.
Found in a hydrothermally-altered peralkaline pegmatite lens in a peripheral part of the ussingite core near its contact with the aegirine-eudialite zone; the pegmatite is part of a larger complex alkaline igneous intrusion.
It is found associated with Microcline, sodalite, arfvedsonite, sphalerite, pectolite-sérandite, mangan-neptunite, murmanite, vigrishinite, epistolite, belovite-(Ce), steenstrupine.
The mineral was named to honor Russian crystallographer, crystal chemist and physicist Boris Borisovich Zvyagin (1921-2002), who was a pioneer and expert in electron diffraction studies of materials.