Nechelyustovite
Nechelyustovite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Na ) ₂Ba₄Ti₄Nb₄(Na₁₁ )Ti₄(Si₂O₇)₈O₈(OH)₈(H₂O)₁₂.
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 3; specific gravity 3.32–3.42; White streak; Vitreous, pearly, or silvery luster; optically biaxial.
IMA symbol Nec, IMA status: approved, named in 2006.
From the natrolite core of hydrothermally altered pegmatite emplaced in nepheline syenites near their contact with ijolite-urtites.
It is found associated with Natrolite, belovite-(La), belovite-(Ce), gaidonnayite, nenadkevichite, epididymite, fluorapophyllite, sphalerite, barytolamprophyllite.
The mineral was named to honor Georgii N. Nechelyustov (b. 1939), Russian electron microprobe analyst.