White terskite associated to brown kentbrooksite from a pegmatite in Russia (Yubileinaya Pegmatite, Lovozero Massif, Kola, Russian Federation). — Photo: David Hospital · CC BY-SA 4.0
Terskite
Terskite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₄ZrSi₆O₁₆·2H₂O.
It crystallizes in the orthorhombic crystal system (space group Pnc2). It is a member of the Terskite structural group.
Key properties: Mohs hardness 5; specific gravity 2.71; Vitreous luster; optically biaxial.
IMA symbol Ter, IMA status: approved, named in 1982.
Found in veins in pegmatites in alkalic massifs.
It is found associated with Potassic feldspar, sodalite, davyne, arfvedsonite, aegirine, eudialyte (Mt. Alluaiv, Russia); villiaumite, ussingite, gmelinite, tetranatrolite, epistolite.
The name refers to the Tersk shore of the White Sea, southeastern Kola Peninsula, Russia.